Background: Despite reports of high rates of suicidal behavior among mentally ill homeless persons, it remains unknown whether the well-established suicide risks of increased age and comorbid psychiatric and substance abuse disorders ("dual diagnosis") documented in the general population are also markers for increased suicide risk among homeless persons.
Methods: Data from a multi-site outreach program (ACCESS) (N = 7,224) were used to investigate whether rates of serious suicidal ideation and recent suicide attempts varied with the age and substance abuse diagnosis(es) (drug abuse and/or alcohol abuse disorders) among homeless mentally ill clients.
Results: The prevalence of 30-day suicidal ideation and suicide attempts (37.5 % and 7.9 %, respectively) was extremely high. Although the risk of serious suicidal ideation and suicide attempts was greater among the younger compared with the older homeless mentally ill clients, risks were not significantly increased by co-morbid alcohol and/or drug abuse. However, a significant interaction between age and co-morbid substance abuse was observed showing that among older clients but not younger clients, those with drug and alcohol abuse were at significantly greater risk of suicidal ideation than those without substance use problems, controlling for confounding factors.
Conclusion: Efforts to prevent suicide should recognize that among homeless people with mental illness, young-middle-aged (30- to 39-year-old) clients are at greatest risk of suicidal behavior. Among older clients the presence of both drug and alcohol abuse significantly increases suicide risk. These patterns are of special importance because they are quite different from those that are well documented in non-homeless populations.