Suicide and self-harm following prescription of SSRIs and other antidepressants: confounding by indication.
OBJECTIVE
To identify the incidence and risk of suicide and self harm, among patients prescribed antidepressant drugs.


METHODS
A retrospective cohort study, with nested case control, of patients identified from a nonrandom sample of general practices in New Zealand from 1996 to 2001. A total of 57 361 patients who received a prescription for a single antidepressant were identified from the RNZCGP Research Unit Database. Suicides within 120 days of a prescription were identified from the New Zealand National Mortality Database and self-harm events within 120 days of a prescription were identified from the New Zealand Hospital discharge database.


RESULTS
26 suicides and 330 episodes of self-harm were identified within 120 days of an antidepressant prescription. On univariate analysis the association, expressed as OR (95% CI), between selective serotonin reuptake inhibitors (SSRIs) and self harm and suicide were 2.26 (1.27-4.76) and 1.92 (0.77-4.83), respectively. When corrected for the confounding effects of age, gender and depression/suicidal ideation there was an association between SSRIs and self harm, OR 1.66 (95% CI 1.23-2.23), but not for suicide, 1.28 (0.38-4.35). Paroxetine was a significant risk factor for suicide on univariate analysis, 4.23 (1.19-14.95), but not when corrected for age, gender and depression/suicidal ideation, 2.76 (0.30-24.87).


CONCLUSIONS
Age, gender and pre-existing depression/suicidal ideation are important confounders in observational studies of the association between antidepressants and suicide or self harm.
Didham
Rebecca C
RC
Research Unit, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
McConnell
Doug W
DW
Blair
Hayden J
HJ
Reith
David M
DM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000928:Antidepressive Agents / Q000009:adverse effects*; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D016728:Self-Injurious Behavior / Q000139:chemically induced* / Q000453:epidemiology; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects*; D013405:Suicide / Q000706:statistics & numerical data*
D000928:Antidepressive Agents; D017367:Selective Serotonin Reuptake Inhibitors