SAD Study - SAD Light Therapy Reasearch

Other Considerations

The recall of lifetime episodes of seasonal depression is affected by the time of year the interview takes place; that is, patients interviewed during autumn or winter are more likely to report lifetime seasonal difficulties as compared to patients interviewed in the summer (Lam & Levitt, 1999).

A study carried out in the UK showed a prevalence rate of SAD was calculated to be 2.4% according to the strictest DSM IV criteria (American Psychiatric Association, 1994). The majority of identified cases had not previously received a diagnosis of SAD from their general practitioner, although over half had been diagnosed with other forms of depression and had been prescribed antidepressant medication. Therefore although SAD was found to be common in the general population sample it appeared to be largely under-diagnosed and/or misdiagnosed (Michalak et al, 2001).

One USA study, which used a structured diagnostic interview, reported that SAD patients were more educated than non-SAD patients, and that it was more common in rural settings. However, a Canadian study, which used a similar diagnostic interview, found no urban-rural or educational effects.