Non-linear relationships in associations of depression and anxiety with alcohol use

Background. Many studies have demonstrated co-morbidity of alcohol abuse/de pendence with mood and anxiety disorders but relatively little is known abo ut anxiety and depression across the full continua of alcohol consumption a nd problems associated with drinking. Methods. Participants from a general population sample (N = 2725) aged 18-8 0 years completed the Alcohol Use Disorders Identification Test (AUDIT) and four measures of negative affect (two depression and two anxiety symptom s cales) included in a self-completion questionnaire. Results. High consumption, AUDIT total score, and AUDIT problems score were associated with high negative affect scores in participants under 60 years old (ORs in the range 1.80-2.83). Graphical and statistical analyses using continuous measures of alcohol use/problems and negative affect identified non-linear relationships where abstainers and occasional drinkers, as well as heavy and problem drinkers, were at risk of high anxiety and depression levels. This pattern, however, was not found in those aged greater than or equal to 60 years. The U-shaped relationship was not an artefact of abstai ners being typical of the general population in their distribution of negat ive affect. Conclusions. Studies of co-morbidity should acknowledge the possibility of non-linear associations and employ both continuous and discrete measures. A bstainers, as well as heavy drinkers, are at increased risk of symptoms of depression and anxiety disorders. Psychosocial factors may play a role in t he U-shaped relationship between alcohol consumption and mortality.