Friday August 28 2009
Heavy drinking is not better for mental health than abstinence
"Teetotallers suffer higher levels of depression than drinkers,” reported The Daily Telegraph. Scientists have found that people who abstain are also more likely to lack social skills, have higher levels of anxiety and have more mental health issues than “those considered heavy drinkers”, said The Daily Telegraph's story on alcohol and depression.
The results from this large population study in Norway of 38,390 people show an increased risk of anxiety and depression for abstainers, and for those who drink heavily.
However, it cannot explain why abstainers and low-level alcohol consumers may have a higher risk of common mental disorders. Although the study cannot prove causation, it has some strengths, including taking into account many social and health factors that could have confounded this association. Importantly, a person may be drinking low or high levels of alcohol as a result of their anxiety or depression, rather than the other way round. This study does not prove that low alcohol consumption causes depression and does not endorse a lifestyle of heavy drinking as being better for mental health than abstinence.
Where did the story come from?
The research was carried out by Jens Christoffer Skogen and colleagues from universities, hospitals and other institutions in Norway. The first author received support from members of the Network of Psychiatric Epidemiology (NEPE) and Sverre Nesvåg at Alcohol and Drug Research Western Norway. Another author was supported by the Biomedical Research Centre for Mental Health at the Institute of Psychiatry, Kings College London and the South London and Maudsley NHS Foundation Trust. The study was published in the peer-reviewed medical journal Addiction.
What kind of scientific study was this?
This cross-sectional study examined the association between levels of anxiety and depression and alcohol consumption. It tested the theory of a “U-shaped relationship” between drinking and mental health disorders, where abstainers and heavy drinkers have an increased risk of anxiety and depression compared to moderate drinkers.
Researchers used data from both the first and second Nord-Trøndelag Health Studies (HUNT). HUNT-1, conducted between 1984 and 1986, established a database of health-related information for all people aged 20 or over living in the Nord-Trøndelag County. In 1995-97 the same population was assessed in HUNT-2. In total, 93,000 individuals were eligible to participate in the HUNT studies, and 67% of the men and 76% of the women taking part in HUNT-1 also took part in HUNT-2.
In these analyses, the researchers included all participants of HUNT-2 who gave information about alcohol consumption, mental health and potential confounders. The analyses included 38,390 people, which is 41% of the total eligible population.
Drinking level was measured by a questionnaire that assessed alcohol consumption over a two-week period. Alcohol consumption was assessed by alcohol units, one unit being equivalent to a 35cl bottle of beer (4.5%), a 12cl glass of wine (12%) or a 4cl shot of spirits (45%).
Abstainers were identified by being asked the question, “Are you an abstainer?”, and as people who reported no alcohol consumption during the two-week period. Those who said they were an abstainer but reported drinking alcohol were classified according to their reported consumption (there were 41 such people) and those who did not report drinking any alcohol but said they were not an abstainer were classified as “non-consumers”.
Alcohol drinkers were categorised into gender-specific percentiles of consumption.
Anxiety and depression were measured using a validated rating scale (timing of assessment not reported). Potential confounding factors that can influence both alcohol consumption and risk of mental health problems were accounted for in analyses. These included gender, age and social class.
In a sub-sample of 20,337 people, heavy drinking was also assessed for the previous 11 years in those who were current abstainers. This was to examine the risk of mental health problems being related to a previous heavy drinking habit (termed “sick-quitting”).
What were the results of the study?
In the total sample of 38,390 people there were 4,446 (11.6%) self-reported alcohol abstainers and 8,570 (22.3%) who did not regularly drink alcohol but did not consider themselves to be abstainers (non-consumers). Alcohol abstainers were more commonly female, older and had more chronic illness than non-consumers and moderate consumers.
When sick-quitting was assessed, current abstainers had mostly been non-consumers (58.1%) or abstainers (30.9%), but rarely high consumers (1.5%) in the previous 11 years.
The researchers found the expected U-shaped association between alcohol consumption and the risk of anxiety and depression. Compared to moderate drinkers, abstainers from alcohol had increased risk of anxiety (OR 1.34, 95% CI 1.19 to 1.52 [adjusted for age and gender]) and of depression (OR 1.52, 95% CI 1.30 to 1.77).
Adjusting for socioeconomic status, social network, other illness, sick-quitting, age (depression only) and gender (anxiety only) slightly lessened the strength of this association, but it remained significant. The risk for abstainers was slightly greater than for those who reported no usual alcohol consumption in a two-week period, but did not label themselves as abstainers.
What interpretations did the researchers draw from these results?
The researchers conclude that the risk of anxiety and depression is increased in people who drink low levels of alcohol compared to those who drink moderately. In particular, risk increased for individuals who label themselves as abstainers.
What does the NHS Knowledge Service make of this study?
This large cross-sectional study of a Norwegian population demonstrated an association between depression and anxiety, and both abstaining from alcohol and heavy drinking. Efforts were made to take into account many social and health factors that might confound this association, and also the possibility that current anxiety or depression in an abstainer may reflect a previous heavy drinking problem.
However, cross-sectional studies such as this cannot prove causation. People may drink low or high levels of alcohol because of their anxiety or depression, so the results do not necessarily mean that alcohol consumption was the cause of the mental disorder. In addition, different people are likely to report their alcohol consumption in different ways, and there is possibly some bias in the way people with anxiety or depression report their alcohol use.
As such, the results provide little information on why abstainers and low-level alcohol consumers may have a higher risk of some mental health problems. As the authors say, it is not possible to speculate from this study about the relationship between alcohol consumption and other mental or general health conditions, as only depression and anxiety were assessed.
News reports that non-drinkers have more mental health issues than heavy drinkers are an inaccurate reflection of this study’s findings. Those who drank heavily also had increased risk of anxiety and depression. Aside from mental health, the health risks associated with heavy drinking are also well established. The study findings do not endorse a lifestyle of heavy drinking as being better for mental health than abstinence.