Alcohol Use Marker May Also Signal Marijuana Use, Risk of Depression

An enzyme whose activity is affected by alcohol may prove useful in identifying recent alcohol or marijuna use even though it does not seem to be a good marker for genetic predisposition to alcoholism, a new international study finds.

The researchers also found that the activity level of the enzyme, adenylyl cyclase, steadily dropped in people who had abstained from drinking for days to weeks and was generally lower in people with a history of major depression, according to the study published in the July issue of Alcoholism: Clinical and Experimental Research.

Previous research has shown an association between a family history of alcoholism and lower activity levels of adenylyl cyclase, says lead author Paula L. Hoffman, Ph.D., of the University of Colorado Health Sciences Center.

This study, which had a much larger sample size than previous research, shows that the effect of genetic susceptibility to alcoholism on this enzyme's activity levels is lost in the wake of the more substantial influence of recent alcohol use.

The study included nearly 1,500 subjects in five countries. Researchers interviewed and categorized participants as alcohol dependent or alcohol abusers, based on standard criteria. The researchers used blood tests to measure adenylyl cyclase levels along with other markers known to reflect alcohol use.

Adenylyl cyclase activity was more sensitive to alcohol consumption in subjects with a family history of alcoholism than in those without such a genetic susceptibility. However, the activity levels fluctuated so much and proved most sensitive to recent drinking, i.e. in the past week, that it was not a consistent measure for assessing family history.

The researchers also found that adenylyl cyclase activity levels were substantially higher in chronic marijuana users; they suggest this may be a product of marijuana use or an abnormal metabolism in those prone to abusing the drug.

People with a history of major depression were also more likely to have low adenylyl cyclase activity levels, a finding that may point to one genetic factor in depression, the authors say.

This study was conducted as part of the WHO/ISBRA Study on State and Trait Markers of Alcohol Use and Dependence.