Light therapy, consisting of exposure to bright light in the morning, has been successful in relieving symptoms of

The right answer is seasonal affective disorder.

Seasonal affective disorder is associated with seasonal variations in light intensity. In winter, we live mostly indoors and are exposed to less natural light. Research indicates that this lack of sun exposure disrupts the function of a brain neurotransmitter called serotonin. This disturbance can induce a depressive state.

Seasonal affective disorder improves in the spring. About one-third of people who suffer from seasonal affective disorder even have moods that increase slightly in the spring or summer (hypomania).