While seasonal affective disorder is often cited as a problem for many during the winter months, researchers have found that suicides and mental health problems peak during summertime. 'It certainly deserves more study, certainly deserves more concern,' Norman Rosenthal, the psychiatrist who first described seasonal affective disorder, has said. Whereas winter depressives may tend to oversleep, overeat and feel sluggish, summer depressives may feel insomnia and have a lesser appetite. Researchers also note that summer depressives tend to be more agitated, rather than the lethargy shown in winter depressives. The key to the disturbing trend may be in energy levels, according to Rosenthal, who is publishing a book on the disorder.