Foundation URI : http://id.who.int/icd/entity/822487798 ICD-11 Criteria For Seasonal Pattern Of Mood Episode Onset 6A80.4  Description In the context of recurrent depressive disorder, bipolar type I or bipolar type II disorder, there has been a regular seasonal pattern of onset and remission of at least one type of episode (i.e., depressive, manic, mixed, or hypomanic episodes), with a substantial majority of the relevant mood episodes corresponding to the seasonal pattern. (In bipolar type I and bipolar type II disorder, all types of mood episodes may not follow this pattern.) A seasonal pattern should be differentiated from an episode that is coincidental with a particular season but predominantly related to a psychological stressor that regularly occurs at that time of the year (e.g., seasonal unemployment). Diagnostic Requirements This specifier can be applied if: In the context of Bipolar Type I or Bipolar Type II Disorder there has been a regular seasonal pattern of onset and rem

Seasonality Effect The seasonality effect in schizophrenia refers to the observation that the symptoms of schizophrenia appear to follow a seasonal pattern, with an increased incidence of relapse or exacerbation of symptoms during specific times of the year, such as winter. One study that investigated the seasonality effect in schizophrenia found that hospital admission rates for patients with schizophrenia were highest in the winter months and lowest in the summer months (Weiser et al., 2005). Another study found similar results, with a higher frequency of psychosis relapses in winter compared to summer months (Kilbane et al., 1996). Additionally, research has suggested that low levels of sunlight, which is more common in winter months, may play a role in the seasonal variation of symptoms in schizophrenia. For example, a study showed that exposure to bright light therapy was associated with a decrease in the severity of symptoms in patients with schizophrenia (Levine et al., 1998).