'Clock' gene linked to symptoms.

• Position: Depression

Depression appears to be associated with a molecular-level disturbance in the body's 24-hour clock, posits a study published in the Journal of Affective Disorders.

Scientists examined genes that regulate circadian rhythm in people with and without a history of depression. As a group, those with a history of depression have a higher level of activity of the so-called clock gene, which has a role in regulating circadian rhythm, than do people with no mood disorders.

Higher expression levels of this gene suggest something is amiss in the body's 24-hour biological and behavioral cycle, which could affect sleep patterns and other physiological functions governed by circadian rhythm. Sleep disturbance is a common symptom of depression.

However, the researchers note that the association between the gene activity and depression is just that--a link, with no demonstrated causal effect in either direction.

At this point concerning what is known about the relationship, this genetic profile could lead to depression or depression could alter this particular gene function, or some other biological or environmental influences could combine to disrupt the circadian clock.

Though this study offers just a snapshot of time in circadian activity in people with and without depression...