The aims of this study were to assess the association between gabapentin and suicidality in patients diagnosed with bipolar disorder (BD) and to determine whether the risk is greater relative to patients prescribed lithium. This retrospective observational study utilizes US population-based claims data assembled by PharMetrics Inc., comprising 47 918 patients diagnosed with BD. Patients were included if they were at least 18 years old and initiated a new monotherapy prescription of either gabapentin (n=2421) or lithium (n=3101). Patients were followed for up to 1 year. Gabapentin patients contributed 915.8 person-years (PY) of follow-up time; lithium patients contributed 1421.3 PY. There were 21 suicide/self-harm events in the gabapentin group and 16 in the lithium group. Unadjusted incidence rates were 22.9 and 11.3/1000 PY in the gabapentin and lithium groups, respectively (P=0.03). After adjusting for concomitant medications, comorbid diagnoses, age, sex, and history of suicide/self-harm, the hazard ratio was 2.3 (95% confidence interval: 1.2–4.5). A propensity score-matched analysis accounting for pre-existing illnesses and medications supports this finding, with an adjusted hazard ratio of 2.1 (95% confidence interval: 1.02–4.5). Relative to lithium, the use of gabapentin is significantly associated with a doubling of the risk of suicidality in patients diagnosed with BD.
aForensic Research & Analysis, Lake Oswego
bSchool of Public Health
cDepartment of Psychiatry, Oregon Health and Science University, Portland, Oregon, USA
Correspondence to Wendy M. Leith, MS, MPH, Forensic Research & Analysis, 4500 Kruse Way, Kruse Plaza I, Suite 385, Lake Oswego, OR 97035, USA Tel: +1 971 255 1008; fax: +1 971 255 1046; e-mail: firstname.lastname@example.org
Received June 5, 2018
Accepted October 16, 2018