I always ask patients about drug and alcohol use.
Often times, someone will tell me that they drink alcohol or smoke marijuana "socially" or "on weekends" or "average". I always follow this up with more questions about how much this really amounts to.
Often times, this amounts to a pattern of either daily use, or quite frequently of having binges at least once a month, sometimes once or more per week.
It is quite clear from a medical point of view that binge drinking is psychologically harmful: not only does it place someone in a position of higher risk for physical accidents (I do not have to search my memory far to think of tragic alcohol-related deaths or severe head injuries among young students in the prime of their life), the pharmacological effect of this type of usage will exacerbate all mood and anxiety problems. It will interfere with normal sleep for long periods of time after the binge is over, and if there is a mood-related or anxiety-related sleep problem already, it can push the symptom intensity up much higher and make it much more difficult to treat.
I have found that many people, upon describing their pattern of binge drinking or marijuana use, will say that their behaviour is part of normal, ubiquitous university culture, i.e. "everyone does it."
Here is what some statistics show from a local part of a large recent continent-wide survey of university students:
Percentage of students who actually have never used marijuana: 63%
Students' belief about what percentage of fellow students have never used marijuana: 16%
Percentage of students who actually use marijuana daily: 1 %
Students' belief about what percentage of fellow students use marijuana daily: 16%
Percentage of students who have actually never used alcohol: 16%
Students' belief about what percentage of fellow students have never used alcohol: 3%
Percentage of students who have used alcohol daily: 0.1%
Students' belief about what percentage of fellow students have used alcohol daily: 30%
All of these above figures show that students greatly overestimate how much their fellow students are drinking and using marijuana. Because of how powerful the influence of social pressure is, especially to young people, it is important to be reminded of the facts. It is much more the "norm" for students to drink or use marijuana rarely, if at all. And it is common -- not rare -- to be completely abstinent.
However, one concerning figure from the same study shows that about 40% of male students, and 30% of female students, have had 5 or more drinks in one sitting at least once in the past month. This is a binge. And this is associated with the greatest risk of physical and psychological harm. For almost 10% of students, binge drinking occurs 3-5 times per month, which is more or less on a weekly basis. This type of behaviour is certainly a prelude to a more severe future of alcoholism, with all its physical and psychological sequelae.
Based on my reading of epidemiological studies, it is clear to me that 2 drinks per 24 hours is the maximum quantity of alcohol reliably consistent with good health (it may be that this level of alcohol consumption actually confers health benefits compared to abstinence, at least for some people).
I am not convinced that any amount of marijuana use is consistent with good health, except perhaps for some people who may have used it just a few isolated times in their lives, in a good mood, in a pleasant environment, which may have helped them relax some of their inhibitions or gain some other insight about themselves or the world. It is more often the case, though, that such experimentation leads to negative health effects.