Affective disorders in young people have been associated with disruptions in circadian rhythms, including abnormalities in secretion of the pineal
hormone melatonin. Previous research reports relationships between pineal gland volumes,
melatonin secretion, and sleep-wake cycles, but the relationship between these factors has not been explored in
affective disorders. This study aimed to characterize these factors and explore associations with mood symptoms and functioning in a sample of young people with
affective disorders. Pineal volume from magnetic resonance imaging and
melatonin assay from evening dim-light saliva collection were evaluated in 50 individuals (15-30 years old; 72 % female) with bipolar, depressive, or
anxiety disorders. Actigraphy monitoring was also conducted for approximately two weeks to derive sleep-wake measures. Pineal volume was associated with
melatonin secretion across the evening, replicating previous findings in psychiatrically healthy individuals. Pineal volume was smaller in participants in which
melatonin onset was not detected. Timing of
melatonin secretion was related to sleep timing, but amount of
melatonin and pineal volume were not related to any sleep-wake measures. A shorter phase angle between onset of
melatonin secretion and sleep onset was associated with longer total sleep time. Lower
melatonin levels were associated with poorer social and occupational functioning. Although pineal volume is not directly related to sleep disturbances or symptoms,
melatonin may influence both sleep-wake cycles and functioning in the early stages of
affective disorder. Causal links remain to be established, however, treatments that target circadian rhythms may be useful in improving functioning in young people with
affective disorders.