Photo: Jay Paul/2009 Jay Paul

While we don’t know all the specifics of Robin Williams’ suicide and probably never will, we do have a broad outline — a decades-long struggle with cocaine and alcohol abuse compounded by bouts of depression — that points to a distressingly common story. Williams’s death, tragic as it is, offers an important opportunity to highlight the connection between substance abuse and suicide — a connection that doesn’t get the attention it deserves.

Researchers have been trying to figure out the causal mechanisms at play for a long time, and there are a great deal of unanswered questions. What we do know with certainty, however, is that there tends to be a great deal of overlap between substance abuse and suicide risk, and that certain substances can contribute significantly to suicide risk in a variety of ways.

As a CDC data brief pointed out in 2011, “Alcohol and drug abuse are second only to depression and other mood disorders as the most frequent risk factors for suicidal behavior.” According to government statistics, about a third of suicide victims test positive for alcohol, while about a fifth test positive for opiates. When the same person has both tendencies toward substance abuse and a mood disorder like depression (shortly after news of Williams’s death broke, his publicist released a statement saying he’d been battling severe depression lately), the results can be devastating.

Alcohol is particularly dangerous for people who may pose a risk to themselves. “When you combine a mood disorder with a drinking problem, the person’s risk is much more erratic — it can go up very quickly once they start drinking,” said Dr. J. John Mann, a Columbia University neuroscientist and vice chair of psychiatry research there. “And if they’re alone, they can become in great danger quickly.”

That’s partly because alcohol — and certain other substances — reduces your inhibitions, making you more likely to do things you wouldn’t do sober. But there are also very specific ways these drugs can interfere with treatment for depression and associated disorders, posing a danger even to those people who are fortunate enough to have access to solid mental health care.

As Dr. David Brent, a University of Pittsburgh suicide researcher, explained, at a neurological level depression appears to have three main components: a diminished response to rewards that saps the amount of pleasure experienced by the sufferer, an exaggerated emotional response to negative events, and an inability to regulate that emotional response after it occurs.

“In terms of psychotherapy, what you focus on is helping somebody to reframe and modulate those responses,” he said. Medication, on the other hand, “tends to focus on diminishing the excessive affective [emotional] response and also increasing the sense of reward” from pleasurable experiences.

Substance abuse can short-circuit much of this. “The drugs affect the brain,” Brent said. “So if you’re trying to use an antidepressant or even psychotherapy to modify the way somebody is thinking and functioning, you’re kind of swimming upstream because there’s evidence that these substances will interfere with some of the same processes that you’re trying to reverse when you’re trying to treat depression.”

People who are depressed and engage in substance abuse aren’t trying to undercut their own treatment, of course — often, they’re self-medicating, simply trying to make day-to-day life a little bit more bearable. But this “bidirectionality,” as researchers call it — the fact that suicidal impulses can lead to substance abuse, and substance abuse can lead to suicidal impulses — makes it very tricky to fully disentangle all the factors that could contribute to an individual’s tendency toward suicide.

Regardless of the specific mechanisms at play, most people understandably associate suicide with mental illness, while perhaps not understanding how potent a risk factor substance abuse is as well. According to Dr. Jane Pearson, a researcher at the National Institutes for Mental Health, that could partly be “because of how our treatment patterns have worked until recently — people with mental health go one place, people with substance abuse go someplace else.” We see these two groups as existing in separate categories, in other words, without understanding how those categories overlap, or that many individuals sit in both at the same time. “Hopefully,” Pearson said, “we’ll have some opportunities within health care reform to have more comprehensive approaches.”

Other than what Williams revealed in interviews, we don’t know a huge amount about how his substance-abuse problems interacted with his thoughts about suicide. All we know is that despite effectively unlimited resources, and despite having fought through his difficulties for decades, building a remarkably successful career in the process, eventually Williams was simply too haunted by whatever was going on in his own head to continue living. There’s a sad lesson here on how formidable an opponent mental illness can be — especially when substance abuse worsens it.