Increasing incidence (e.g. Moore et al. 2019; Stohler et al. 2019) and high economic burden of chronic tinnitus (Maes et al. 2013; Stockdale et al. 2017) demand effective interventions be applied. Chronic tinnitus, the persistent perception of sound (e.g. ringing, humming, or hissing) in the ear(s) or head without corresponding external acoustic source, has no cure. However, cognitive-behavioral therapy (CBT) is strongly recommended (Cima et al. 2019) with a recent Cochrane review supporting its positive effect on participants’ quality of life (Fuller et al. 2020). Based on the Fear Avoidance (FA) model (Fig. 1) of chronic pain (Lethem et al. 1983; Vlaeyen & Linton 2000,2012) adapted to tinnitus (Cima et al. 2011; Kleinstäuber et al. 2013), CBT aims to alter fear cognitions and responses by targeting different steps of the pathological cycle (e.g. catastrophizing, fear, and avoidance) through different techniques (e.g. psycho-education, exposure, and relaxation). CBT for tinnitus may take many forms, as different combinations of techniques may be applied.
Group treatment is an effective form of CBT delivery (e.g. Cima et al. 2012). Despite support for group-based CBT, it is not yet known if the group setting is vital for the effectiveness of CBT for tinnitus. Differences in method of treatment delivery (i.e. group compared to individual therapy) have previously been explored by Fuller et al. (2020) in the context of a meta-analysis. Their analyses revealed that both individual and group-based CBT were more effective than wait list control or “active comparison” conditions, but that there was no difference between individual or group-based delivery. In the meta-analysis, results from studies, using either individual or group-based delivery of different CBT protocols, were not compared directly in one single study. Furthermore, the studies reported mean group-level results, which limits insight into changes during treatment at the individual level. Tinnitus sufferers report high intra- and inter-individual differences (i.e. audiological perception of tinnitus qualities, emotional impact, and distress levels; Henry et al. 2012; Schlee et al. 2016) which may unduly influence results, and which might not be accurately captured through group-level statistical analysis.
To our knowledge, there is no study directly comparing method of delivery of CBT for tinnitus. The current study aims to examine the differences between individual and group treatment. A Single-Case Experimental Design (SCED) is employed to disentangle the treatment delivery methods by exploring the individual path of participants during CBT for tinnitus while alternating between group and individual treatment phases.
Patients on the waiting list for CBT treatment from the Adelante Department of Audiology and Communication (Hoensbroek, The Netherlands) were contacted and invited sequentially to participate in the study. First, patients who had previously volunteered for research on CBT for tinnitus, but could not participate due to scheduling conflicts, were contacted. All other patients on the waiting list for CBT for tinnitus were contacted next (i.e. those on the waiting list longest were invited first).
Potential participants were excluded from participation if they reportedly: (1) were currently undergoing other tinnitus or psychological treatment elsewhere; (2) commenced the use of hearing aids within the previous three months; (3) commenced or ceased the use of antidepressants, antipsychotics, anxiolytics, Ritalin, hormone replacement therapy, or medication to lower high blood pressure within the previous three months; (4) were unable to read and write in Dutch; or (5) disclosed current suicidal intent. In addition, they were excluded if (6) they showed uncorrected hearing loss of 40 dB or more in one or both ears assessed by calculating the Pure Tone Average on 500 Hz, 1000 Hz, and 2000 Hz. A total of six participants were included in the study (Fig. 2). Eligible participants received study information by mail and were contacted by phone to evaluate inclusion/exclusion criteria and an appointment was set up for signing informed consent.
CBT for Tinnitus
The center provides established CBT for tinnitus (for detailed protocol, see Cima et al. 2012). Relying on a stepped care approach, patients first undergo audiological assessment, psycho-educational session, and a psychological intake, as the first step in triage. A multidisciplinary team meeting of the involved professionals determines each patient’s treatment path. Patients are allocated to the more intensive second step of treatment with 2-hour sessions for approximately 10 weeks, if diagnostics showed the more severe patient need. The current study examined the second step of the stepped care approach with bi-weekly treatment delivery of 20 sessions in total. Therapists experienced with the protocol utilized at the rehabilitation center followed the pre-established descriptions of each treatment session.
An adapted multiple-baseline SCED was utilized to examine differences in effects due to the method of delivery by comparing changes in individual and group settings. Compared to traditional Randomized Control Trials (RCTs), the SCED is more appropriate for dissecting treatment components (e.g. method of delivery) as all participants undergo the isolated components (i.e. in this case, individual and group setting) during different phases of the treatment (Krasny-Pacini & Evans 2018). More specifically, after a baseline (phase A), each participant underwent the same treatment protocol in two different sequential orders (BC versus CB): individual (phase B) or group (phase C). The usual multiple-baseline design relies on a bi-phasic A–B design and randomizes the baseline length (A) to increase power for comparisons with a subsequent treatment phase (B). The design utilized in this study randomizes the length of each treatment phase instead of baseline. The adaptation takes into consideration the research question of comparing treatment settings to each other rather than comparing treatment effectiveness to a no-treatment baseline. Three random paired schedules with a minimum of 14 observations per treatment phase (Fig. 3) were randomly drawn using a dedicated Single-Case Data Analysis app (SCDA; Bulté & Onghena 2013; De et al. 2020), from a total of 477,042 permutations (minimal possible p = 2.1 × 10−6). For each participant commencing the treatment in the group setting, a paired participant was allocated to the individual setting. At randomly designated start dates of the relevant treatment setting, paired participants switched settings. This specific design guaranteed that a minimum of three participants were always allocated to group treatment, thereby maintaining the number of participants required to ensure true in-group experience. The first treatment session took place on October 9, 2019, for all participants. The last treatment session was held on December 13, 2019. Three-month follow-up data collection, planned for March 2020, was disrupted by the COVID-19 pandemic and therefore was slightly delayed and took place from May to July 2020. No blinding was utilized. Furthermore, the treatment delivery team remained constant throughout the study regardless of the treatment setting (i.e. lead therapist provided both individual and group sessions following a strict therapy manual).
The research was approved by the Nationally appointed Medical Ethical Committee at Maxima Medical Centre, in Veldhoven, the Netherlands, as part of a larger project (METC; NL63262.016.18) and registered at the Dutch Trial Register (NL8056). Reporting follows guidelines established at SCRIBE (Tate et al. 2016).
End-of-day diary (EDD) data were collected from baseline to the end of the treatment (79 days). The diary was delivered through a purpose-built app installed on participants’ smartphones (mEMA; ilumivu, Inc., Cambridge, MA, USA; www.ilumivu.com). EDD assessments took place at 8 P.M. every night (with a 4-hour time limit for completion), and consisted of 15 questions regarding different aspects of the tinnitus experience (i.e. annoyance, interference, distraction, anger, invasiveness, sadness, activity levels, fear, avoidance, masking, and pleasantness) and overall well-being (i.e. happiness, anxiety, sleep quality, social interaction, and stress). All questions were rated on a seven-point Likert scale (0 to 6), except for social interaction (“Who did you spend time with today?”), which presented the participant with seven mutually non-exclusive options (“nobody,” “partner,” “family,” “friends,” “colleagues,” “acquaintances,” and “strangers”).
Standardized Outcomes and Self-Reported Goals
Standardized outcomes were collected before treatment onset (T0), after the end of the full treatment protocol (T1), and follow-up (T2).
Tinnitus Functional Index (TFI; Meikle et al. 2012) is an assessment of tinnitus impairment in daily functioning. The TFI was specifically designed as an outcome measure for clinical trials. Consisting of 25 items, this self-report tool relies on 10-point Likert scales to classify tinnitus-related impairment experienced over the previous week (e.g. What percentage of your time awake were you annoyed by your tinnitus?). Higher scores reflect greater impairment and a 13-point change is considered clinically meaningful. The tool is divided into eight subscales: intrusiveness; sense of control; cognitive interference; sleep disturbance; auditory difficulties due to tinnitus; interference in relaxation; quality of life; and emotional distress. The Dutch version of TFI was used (Rabau et al. 2014).
The Tinnitus Questionnaire (TQ; Hallam et al. 1988) is a widely used questionnaire for the assessment of tinnitus severity (Hall et al. 2016). Fifty-two items are rated on a three-point scale for an overall score indicating tinnitus distress (e.g. The noises have affected my concentration). Meeus, Blaivie and Van de Heyning (2007) validated the TQ in Dutch. Despite a minimal change of five points being commonly considered clinically relevant (Kleinjung et al. 2007), a more conservative 12-point change approach is used at present (Hall et al. 2018).
The Fear of Tinnitus Questionnaire (FTQ; Cima et al. 2011) is a 17-item list of fear-related statements regarding tinnitus experience (e.g. I fear that my tinnitus is the result of a tumor). The tool is reliable, valid, and responsive to clinical change (Fuller et al. 2019), with higher scores, obtained by the number of responder-selected items (judged to be true for them) in the list, being correlated with higher interference in daily life.
The Tinnitus Catastrophizing Scale (TCS; Cima et al. 2011) is an adaptation of the Pain Catastrophizing Scale (Sullivan et al. 1995). The TCS consists of 13 items on a five-point Likert scale, the PCS aims at assessing catastrophizing cognitions and misinterpretations related to pain (e.g. I feel I can’t go on). Items have been adapted by replacing pain-related items with tinnitus equivalents. The TCS has been previously used in a large RCT on CBT for tinnitus patients (Cima et al. 2012) and it was shown that increased scores on the TCS are associated with decreased quality of life, increased tinnitus severity, increased fear for tinnitus, and increased negative general affect.
The Chronic Tinnitus Acceptance Questionnaire (CTAQ; Moreland 2007) is a 20-item self-report assessment on a seven-point Likert scale adapted from the Chronic Pain Acceptance Questionnaire (CPAQ; McCracken et al. 2004,2005). This scale assesses participation in everyday activities despite tinnitus experience as well as the acceptance of the tinnitus experience without avoiding it (e.g. I am getting on with the business of living no matter what my level of tinnitus is). Lower scores reflect poorer levels of chronic tinnitus acceptance.
The Depression Anxiety and Stress Scale-21 (DASS-21; Lovibond & Lovibond 1995) is a widely used measure of emotional wellbeing. With excellent psychometric properties (Antony et al. 1998), the tool consists of 21 items on a four-point Likert scale to measure symptoms of depression, anxiety, and stress with higher scores indicating worsening of depression (e.g. I felt I wasn’t worth much as a person), anxiety (e.g. I felt I was close to panic), and stress (e.g. I found it difficult to relax). A revised Dutch version (de Beurs et al. 2001) was utilized in the current study.
Interpersonal Needs Questionnaire (INQ-15; Van Orden et al. 2012) is a 15-item, self-report questionnaire, which uses a seven-point Likert-type scale. The questionnaire measures an individual’s social disability/inclusion through two subscales: perceived interpersonal measures of relationship distress (perceived alienation; e.g. These days, I feel like I belong) and self-perceived burden to others (e.g. These days the people in my life would be happier without me). Higher scores are associated with higher levels of perceived alienation and burden.
Personal goals of treatment outcomes were set through a semi-structured interview performed at T0. Participants were asked to describe their tinnitus disability (e.g. how they were negatively impacted by their tinnitus) and then set personal therapeutic goals by answering the question: What would you like to be improved at the end of the therapy?
Goal attainment and maintenance were confirmed at T1 and T2 by asking participants to describe the personal effect of treatment, whether tinnitus disability had diminished, and if there was improvement noticed. Personal goals set at T0 were then discussed and progress evaluated.
Data collected from EDD was plotted through time with level (i.e. central tendency), variability, and trend visually inspected. Broadened medians (Rosenberger & Gasko 1983), an outlier-resistant alternative to means and more robust against outliers, were used to assist with a visual inspection of levels. Variability was inspected with the aid of range lines drawn from the highest and lowest scores per phase. Least Squares regression was used to visually inspect the trend per phase. Influence of outliers was reduced conservatively by removing a singularly occurring highest and/or lowest score on a particular item per phase per participant for the visual inspection of variability (trimmed range; Morley & Adams 1991). This approach was also applied for the inspection of trend.
Social interaction was separately analyzed with each answer (“partner,” “family,” “friends,” “colleagues,” “acquaintances,” and “strangers”) recorded into dichotomous variables (0 = no contact; 1 = contact). Each new variable was plotted through time and visually inspected for differences in level (broadened median) between phases B and C.
Effect Size Calculations
Non-overlap of all pairs (NAP; Parker & Vannest 2009) was utilized to calculate effect sizes between all phases. Cutoffs for NAP effect sizes can be interpreted as small (<0.66), medium (>0.65 and <0.93) or large (NAP > 0.92). In a second step, trend was taken into account when calculating NAP between individual and group phases by utilizing Tau-U (Parker et al. 2011), a combination of Kendall’s rank correlation test (Tau), and Mann-Whitney statistics (U).
Randomization Tests (RT)
Differences between individual (B) and group (C) treatment were calculated through Randomization Tests (RT) with Monte Carlo sampling (1000) and test statistics defined as (the absolute difference between the means of B phase observations and the means of C phase observations) since no specific direction of change was hypothesized (Onghena & Edgington 2005).
Standardized Outcomes and Self-Reported Goals
Effects of the treatments were tested by examining changes in scores on the TQ and TFI. Differences between T0 and T1, as well as T1 and T2 were calculated for each participant. Personalized goals of treatment outcomes at T0 were assessed at T1 and T2.
All other standardized outcomes (i.e. FTQ, TCS, CTAQ, DASS-21, and INQ) from baseline are reported.
Software and Output
All visual plots and analyses, as well as RTs, were calculated through the online SCDA app (Bulté & Onghena 2013; De et al. 2020). NAP and Tau-U analyses utilized “Single-Case Research: web-based calculators for SCR analysis (Version 2.0)” (Vannest et al. 2016).
Visual inspection plots of the EDD scores for all items are presented in the supplemental material.
Demographic data of the six participants at the onset of the study are presented in Table 1. One participant (P5) commenced the use of a hearing aid on October 2 and was allowed to participate. A follow-up interview of this participant revealed that the hearing aid was seldomly used, specifically when in silence. Data for this participant were analyzed as planned as changes were not attributable to the hearing aid by the participant. One female participant (50 years old) dropped out during the second week of treatment due to personal reasons unrelated to tinnitus. To maintain a minimum of three participants during group treatment, one patient (male, 49 years old) who was indicated for CBT for tinnitus and next on the waiting list, was added to and participated in group treatment, while exempted from data collection. Participant P2 missed the highest number of diary entries (26.3%) due to planned holidays. Nevertheless, EDD compliance rates ranged from 73.7 to 98.7% among participants. No adverse events were recorded during treatment.
TABLE 1. -
Demographic and baseline characteristics for scores for Tinnitus Catastrophizing Scale (TCS), Fear of Tinnitus Questionnaire (FTQ), Chronic Tinnitus Acceptance Questionnaire (CTAQ), the sub-scales of the Depression Anxiety and Stress Scale-21 (DASS), and the Burden and Belong sub-scales of the Interpersonal Needs Questionnaire (INQ)
||Hearing aid (time)
||No coinciding factor
||Hearing aid (no effect)
||Both sides of head
||Tinnitus Masking (no effect)
||No hearing aid
||CBT focused on increased physical capacity
||No hearing aid
||No coinciding factor
||In the head
||Traffic (pedestrian) accident
||No treatment focused on tinnitus
Tinnitus Questionnaire (TQ); Tinnitus Functional Index (TFI); Tinnitus Catastrophizing Scale (TCS); Fear of Tinnitus Questionnaire (FTQ); Chronic Tinnitus Acceptance Questionnaire (CTAQ); Depression Anxiety and Stress Scale-21 (DASS); Interpersonal Needs Questionnaire (INQ).
Visual inspection of the level of all variables (broadened median) revealed that all but one participant allocated to the ABC treatment setting order demonstrated no differences between phases or only a small improved level on all variables at the group (C) phase. However, participant P1, in the ABC order, revealed slight worsening during group treatment (phase C) for fear of tinnitus (Fig. 4), while all other variables remained constant or improved as well.
Participants in the alternative ACB order also revealed little to no change variables between phase levels. Most variables’ levels either remained constant or slightly improved at the individual phase (B). On perceived happiness and activity level, participants’ levels decreased in the individual phase (B). No other consistent pattern of change could be identified. All participants’ level of overall perceived social contact remained constant throughout the treatment.
No discernible patterns in variability between phases can be seen. In one participant (P5) variability decreased in all but one item (activity level), while all other participants had no consistent pattern of change in variability across items. Tinnitus avoidance (Fig. 5), interference, sadness, and sleep quality scores were either stable or decreased in variability for all participants. Tinnitus pleasantness decreased in variability across all participants.
Similarly, clear trend patterns between ABC and ACB orders were lacking in the visual inspection. Tinnitus avoidance trend did not change between phases in all participants while all other items presented shifts for at least one participant (e.g. tinnitus annoyance; Fig. 6). Participant (P5) trend improved on five items (activity level, anxiety, tinnitus pleasantness, sleep quality, and stress), while participant (P2) trend improved on four items (tinnitus annoyance, anxiety, tinnitus distraction, and tinnitus invasiveness) after changing treatment phase. Both participants’ improvements were recorded in the second treatment phase – group and individual, respectively. All other participants displayed changes in trends between phases without any discernable pattern.
Low effect sizes (NAP) between baseline (A) and individual (B) treatment were similar to those between baseline (A) and group (C) treatment (Table 2). Without controlling for trends, data overlapped between individual and group treatment. By controlling for trends, Tau-U analysis revealed different significant changes between treatment orders (Table 3). Tinnitus anger, annoyance, fear, interference, invasiveness, sadness, as well as anxiety significantly improved at the group (C) phase for the ABC treatment order. Participants in the ACB order significantly improved tinnitus sadness and worsened happiness and activity levels when in individual (B) treatment.
TABLE 2. -
Non-overlap of all pairs (NAP) effect sizes, and statistical significance based on Tau-U analyses without controlling for trend
A – Baseline, B – Individual treatment, C – Group treatment.
*p < 0.05.
**p < 0.001.
TABLE 3. -
Weighted Tau-U effect sizes, controlling for trend.
||ABC (n = 3)
||ACB (n = 2)
A – Baseline, B – Individual treatment, C – Group treatment.
*p < 0.05.
**p < 0.001.
No significant differences between group and individual treatments for each variable were found in RTs (minimal possible p = 2.1 × 10−6; all p > 0.05).
Standardized Outcomes and Self-Reported Goals
Scores of the TQ and TFI were calculated for each participant (Table 4). A consistent pattern emerged in the results from the pre- to post-treatment phase, which included both individual and group settings in different orders. Four of five participants reported improvements from baseline to after treatment end (T1). The level of improvement exceeded minimally clinically important differences for four participants on the TQ (12-point change), and three of five participants on the TFI (13-point change), with only one participant (P1) not recording improvements in the TQ or TFI from T0 to T1. The sequential order of treatment setting did not have an effect on overall treatment outcome. Furthermore, most objectives set by participants were successfully achieved by the end of treatment (Table 5).
TABLE 4. -
Change in scores of the Tinnitus Questionnaire (TQ) and Tinnitus Functional Index (TFI)
||T1 score (∆T0−T1)
||T2 score (∆T1−T2)
||T1 score (∆T0−T1)
||T2 score (∆T1−T2)
T0 = baseline; T1 = after full treatment; T2 = follow-up.
*Clinically meaningfulchange [TQ (>12); TFI (>13)].
TABLE 5. -
Participants’ self-reported goals and outcomes
||Goals set before treatment (T0)
||Assessment of goals after treatment (T1)
5.Reduce neck pain complaints
|Tinnitus disturbance remained unchanged. Concentration did not improve. Running resumed. Participant continued to apply tinnitus avoidance strategies.
||Overall feeling that tinnitus complaints did not improve or worsened. Sleep improved with more sleeping hours. Other goals did not improve. Gave up on running and switched to walking. Did not practice techniques from treatment (i.e. exposure or relaxation)
3.Improve tinnitus coping
|Participant is generally less concerned with tinnitus and reports more acceptance towards it (in the words of the participant: “I don’t fight it anymore”). Participant experiences tinnitus more clearly in silence, but this subsides and is no longer disturbing. Sleep and concentration improved.
||All positive changes remained. Practices exposure daily. Light sleep problems are not associated with tinnitus.
||1.Less erratic tinnitus and heightened control
2.Diminish influence on function
3.Reduce “fight against tinnitus”
|Feels more “present in the moment” and allows himself experience range of emotions including aversive emotions (e.g. less experiential avoidance). Participant reports using techniques learned at treatment sessions. “Fighting” tinnitus is slightly reduced, although tinnitus is still erratic.
||Worsening of tinnitus complaints since T1. Increased perception of tinnitus triggers irritability, fatigue, and concentration problems. Increased tinnitus complaints are associated with increased workload. Increased work stress due to COVID-19 crisis and rest complaints due to a concussion potentially playing a role. Fear reactions to tinnitus perception and “fighting’ tinnitus decreased. Frequently practices exposure.
3.Reduce burnout feelings
|Participant reports less experiential avoidance and open to aversive emotions. Participant allows himself to experience tinnitus through exposure exercises. Sleep and concentration improved. Increase in assertiveness is associated with reduced burnout
||Sleep deteriorated due to rumination concerning COVID-19 crisis. Tinnitus did not play a role in sleep problems. All other improvements remained. Frequently practices exposure.
||2.Restore balance in mood
3.Regain sense of humor
4.Enjoy silence again
|All objectives were achieved. Tinnitus characteristics remained equal while emotional response changed. Mood is positive again. Regained sense of humor and balanced vigor. Exercises learned during therapy are applied daily.
||All positive changes remained. Often practices techniques learned during treatment.
Follow-up assessments supported the initial patterns found with the exception of one participant (P3), where a clinically meaningful worsening was found in TQ (38 points) and TFI (19.2 points). Another participant (P4) who showed clinically meaningful improvements after treatment further improved at follow-up, reporting clinically meaningful improvements in both TQ (22 points) and TFI (19.6 points) scores.
The current study aims to examine the differences in patient improvements when comparing individual versus group treatment delivery of CBT for chronic disabling tinnitus. The SCED employed is specifically suited to enable direct comparisons between individual and group treatment settings within subjects. Group-based RCTs fail to access the high inter- and intra-individual variability found in tinnitus experience (Henry et al. 2012; Schlee et al. 2016). The SCED allowed us to control for individual conditions which accounted for participants’ idiosyncrasies. Moreover, SCED enabled us to follow participants undergoing both treatment conditions of interest (group and individual CBT), allowing us to test differences as a result of treatment type to be carried out in detail (e.g. assessment of differences in trend, variability, and level).
First, the beneficial effects of CBT were confirmed on the standardized outcome measures collected before, after treatment, and during follow-up. Moreover, clinically meaningful improvements in standardized tinnitus assessments (i.e. TQ and TFI) were found in four out of five participants. The follow-up assessments were delayed for 3 months due to the COVID-19 pandemic. Nevertheless, three of the participants’ improvements were not lost, with one participant improving further after the end of treatment. Semistructured clinical interviews confirmed these changes, with all but one participant reaching the personalized goals set at the beginning of treatment. These findings confirm the effectiveness of CBT for tinnitus, established by Cima et al. (2012), and are in line with current literature on CBT (Fuller et al. 2020) and guidelines (Cima et al. 2019) for tinnitus treatment.
Visual inspection of the data, as well as randomization tests between phases, indicated no significant differences between group and individual treatment. Analyses of data overlap, while accounting for trends, revealed low effect sizes but significant differences between treatments. Participants who started treatment individually and subsequently joined group treatment, showed improvements in the latter when compared with the former. Half of the 14 variables measured held significant differences between phases (tinnitus anger, annoyance, fear, interference, invasiveness, and sadness, as well as anxiety), favoring group treatment. Participants who underwent the opposite treatment order, group treatment followed by individual setting later, only improved further in scores on tinnitus sadness during individual treatment compared to group treatment. Thus, while the group setting increased benefits from treatment on half the variables, the individual setting only provided increased improvements in tinnitus sadness. More importantly, worsening in participants’ happiness and activity levels were observed during the subsequent individual treatment when compared to group treatment. Despite the worsening captured by the EDD, these participants still recorded overall improvements in the standardized outcome measures and clinical interviews (from pre- to post-treatment).
The small differences found between treatment settings are indicative of the potential benefits of group CBT. Unlike individual treatment, group-based treatment may enable social learning, such as observing other patients expose themselves to the feared stimulus (e.g. loud noise, and tinnitus) and challenging the expected outcome (e.g. anxiety and loss of control). Social learning allows for the development of knowledge without the need for first-hand experience, avoiding possible risks of these experiences. Some studies show that seeing someone else expose themselves to a feared stimulus (i.e. vicarious extinction of fear) can lead to superior fear reduction when compared to standard extinction (Golkar et al. 2013,2016).
While most participants improved, one participant (P1) did not benefit from the treatment in either individual or group settings. Moreover, P1 held the highest fear of tinnitus, measured through the standardized questionnaire (i.e. FTQ) and EDD, where high variability was also observed. Fear of tinnitus is known to mediate recovery (Cima et al. 2018) and partly explains treatment efficacy. Tinnitus avoidance, as reported by P1, did not abate during treatment as measured by the EDD and interview, which might explain why fear did not decrease, since the use of safety behaviors to avoid exposure to the feared stimuli may hinder fear extinction (Lovibond et al. 2009). Safety behaviors during tinnitus exposure are difficult to assess, since these might be largely cognitive or interoceptive and therefore cannot be easily observed and controlled for (e.g. patients may use imagery to distract themselves from the tinnitus experience during an exposure exercise). As such, exposure to tinnitus may better resemble Interoceptive Exposure, where the more covert cognitive strategies to avoid the full experience of fear (e.g. relaxation and distraction) may disrupt fear extinction (as reported by P1).
As parallels from chronic pain research may be drawn and inspire the tinnitus field (e.g. the application of the FA model), fundamental research on the underlying mechanisms of chronic tinnitus is in its infancy. Associative fear learning paradigms have been developed and employed in the chronic pain field for decades, enabling the underlying mechanisms of change to be studied (for a review on the development and employment of fear conditioning in chronic pain see Meulders 2020; Vlaeyen & Crombez 2020). While we are able to observe the change in tinnitus experience through CBT, we are only able to speculate on the underlying mechanisms and associative learning models.
Beyond the inherent difficulty in controlling for covert safety behaviors in efficacious exposure exercises, a limitation may be found in the uniqueness of the sample: i.e. five male participants aged between 59 and 66 years old. This homogeneous sample serves as a double-edged sword. Naturally, our findings may not be generalizable to other tinnitus populations at the moment. On the other hand, our outcomes represent robust findings in a specific tinnitus population. The effectiveness of CBT for this specific population is supported, with a group setting presenting a more beneficial treatment type, regardless of hearing aid use or tinnitus duration and location. Treatment response differences between gender have been previously observed, with men more responsive to the combined treatment of Tinnitus Retraining Therapy and CBT (Van der Wal et al. 2020). As such, replication of the protocol with women is a natural step toward tailoring CBT for tinnitus.
CBT for tinnitus is an effective treatment that may be offered in a variety of different methods. Inspired by recent interest in more personalized research and treatment development (Schork 2015; Senn 2018), a SCED was used to explore the differences between group and individual treatment delivery settings of an established CBT for tinnitus protocol (Cima et al. 2012). To our knowledge the current study is the first to directly compare group versus individual CBT in tinnitus patients, revealing that group treatment is potentially more beneficial to participants. While the benefits were observable though small, the underlying mechanism of change (e.g. associative learning models) is yet to be fully explored through fundamental research in the tinnitus field.
M.L. conceived the presented idea. M.L., T.F., S.R., J.V. and R.C. jointly developed the design of the study. S.R. and R.C. developed the study within the clinic. M.L. gathered and analysed data which was verified by T.F. and J.V.. M.L., T.F., S.R., J.V. and R.C. contributed to the final manuscript.
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