The extent to which specific categories of acute substance use are short-term risk factors, or warning signs, for suicide attempts is unknown. The aim of the current study was to quantify the near-term effects of sole use and co-use of substances on medically attended suicide attempts.
The current study used a case-crossover design, comparing substance use within the 24 hours prior to a suicide attempt (case day) to the control day, the matched 24 hours the day prior to the case day. Participants were 363 recent suicide attempters presenting to a Level 1 trauma hospital between October 2008 and April 2014. A timeline follow-back methodology was used to assess acute exposures within the 48 hours before the suicide attempt. Conditional logistic regression was used to report odds ratios (ORs) and 95% confidence intervals (CIs).
Results indicated that patients were at increased odds of attempting suicide after drinking alcohol within a 24-hour period (OR = 4.40; 95% CI, 2.31-8.40) and using a drug from another class of substances with central nervous system (CNS) depressant characteristics (sedatives/anxiolytics and opioids; OR = 2.82; 95% CI, 1.13-7.01), after adjustment for other acute substance use. The acute use of cannabis and CNS stimulants (stimulants/amphetamines and cocaine) was not uniquely associated with suicide attempt. Co-use of alcohol synergized effects of other CNS depressants (OR = 8.76; 95% CI, 1.02-75.44).
Findings suggest the importance of considering acute alcohol use and use of CNS depressants, and the concurrent use of both substances, when evaluating short-term risk for suicide attempts in clinical settings.