The winter-over syndrome is observed in inhabitants of research stations in Antarctica who "winter-over" throughout the Antarctic winter. It consists of a variety of behavioral and medical disturbances, including irritability

Irritability

Irritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli; It is usually used to refer to anger or frustration....

. depression

Depression

Depression or depress may refer to:-Medicine:* Depression , a state of low mood and aversion to activity** Mood disorder, a class of mental illnesses featuring depressed mood...

, insomnia

Insomnia

Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...

 and cognitive impairment.

Possible contributing causes of winter-over syndrome include stress

Stress

- Mechanical :* Stress , the average amount of force exerted per unit area* Compressive stress, the stress applied to materials resulting in their compaction...

, social isolation

Social isolation

Social isolation refers to a lack of contact with society for members of social species. There may be many causes and individuals in numerous generally social species are isolated at times, it need not be a pathological condition. In human society, in those cases where it is viewed as a pathology,...

, subsyndromal seasonal affective disorder and polar T₃ syndrome

Polar T3 syndrome

Polar T3 syndrome is a condition found in polar explorers, caused by a reduction in levels of the thyroid hormone T3. Its effects include forgetfulness, cognitive impairment and mood disturbances. It can exhibit itself in a fugue state known as the "Antarctic stare".It is regarded as one of the...

.