A history of suicide attempts is common in patients entering treatment for substance-abuse problems. A study of 3,733 people beginning treatment for substance abuse in the U.S. found that 9% of them had tried to kill themselves in the year before they started their treatment. In the year after their treatment had finished 'only' 4% of them tried to kill themselves. Suicide attempts made during the course of their treatment were less likely in patients treated in residential as opposed to outpatient settings and a longer course of treatment was associated with a lower likelihood of a post-treatment suicide attempt.
Ilgen, Mark A. ... [et al] - Substance Use-Disorder treatment and a decline in attempted suicide during and after treatment Journal of Studies on Alcohol and Drugs July 2007 68(4), 503-509