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One thing that struck Matt and me when going through the alcohol literature was co-morbidity between heavier alcohol use and a whole pile of other bad things. We wrote:

We also worry that the aetiological fractions used may not account adequately for comorbidity between alcohol use and pre-existing mental disorders. The aetiological fractions used ascribe between twenty-five and thirty percent of male suicides to alcohol; in other words, if alcohol disappeared, the suicide rate would drop by more than a quarter for adult males over the age of twenty. As alcohol use can often be a form of self-medication among those with mental illness, whether alcohol plays that substantial a
causal role in suicides is debatable. Ross (1995) finds that more than half of those with an alcohol disorder have a lifetime comorbid psychiatric disorder. Among subcategories for which data is presented, alcohol abusers have rates of mood disorders and anxiety disorders 2.3 and 1.7 times that of non-abusers. While 9% of alcohol abusers report antisocial personality disorders, only 0.6%  of non abusers report such disorders. The Mental Illness Fellowship of Australia (2005) notes that those with bipolar disorder are eleven times more likely to engage in harmful drug or alcohol use than is the general population. Kessler et al (1997) find that those with long term alcohol abuse or dependence not only have a high probability of also exhibiting another mental disorder but also that comorbid DSM-IIIR disorders tend to predate alcohol use disorders.  
Some people with pre-existing disorders self-medicate with alcohol and consequently are better off than they would have been but worse off than average; their variance from average outcomes is counted as a cost of alcohol. Some people with pre-existing disorders self-medicate with alcohol and consequently are worse off than they otherwise would be; the total amount of their variance from average outcomes is counted as a cost of alcohol rather than only the incremental worsening from their individual baselines. This stuff isn't easy. But the direction of the bias is pretty clear.

Emma Hart at Up Front [not guaranteed safe for work] points to more work in similar vein: bisexuals are more likely to have problems with binge drinking. And it's because of underlying social pressures. She writes:
Here’s a clue, guys: it’s not the drinking, it’s the why they’re drinking. Take a lesson from gaynz.com, and maybe work out why I link to so many stories there instead of at your place: Exclusion Leading Some Bi Youth to Binge Drink. The drinking is not the problem, it’s one of the symptoms of the problem. 
She then quotes from the study's surveys of young binge-drinking bisexuals:
I drink more when I’m under high stress, when I’m stressed out, and maybe sometimes at parties when, after conversations with people, where they want to know, no one gets the bi thing. It’s really hard to explain. Quite a bit because you get people who want to know why you are not lesbian, why you are not straight, and I kind of feel that, it’s slightly easier to be one or the other, like I envy some of my friends who are gay, I’m like you know who, you know you’re there and no one questions it. But I get questioned all the time, and I find that frustrating sometimes.
...
Arahia: You kind of drink more so you can say the next day: “Oh, I was just drunk, you know. It didn’t mean anything really.” Sometimes it does, sometimes. But if you wake up the next morning with a huge hangover, you can say to the person: “Oh god, it didn’t mean anything. I was just so wasted.”

Fiona: “Didn’t mean to grope you. I was just drunk.”

Arahia: It is such a good excuse.

Fiona: And I think bi people definitely use it as more of an excuse than any other sexual orientation.
Sometimes, use of alcohol is inframarginal to whatever other behaviour we're measuring, whether crime or sex. Sometimes, alcohol use helps people to get over their inhibitions and do utility-enhancing things. And, sometimes alcohol use leads people to make mistakes. We overstate the costs of alcohol when we assume that alcohol's role is always causal and always negative, or when we assume away the positive consequences.

SciBlogs note: Alcohol disclosures here.