Lepine et al are the third group from countries in both the Northern and Southern Hemispheres1 to report that patients with panic disorder have panic onset more often in late spring and summer than in fall or winter. This seasonal bias, and it's possible link with suicidal ideation and attempts, is, however, only one of many factors associated with the timing of first panics; others include heat, light, being in a situation from the agoraphobic cluster, life events, tiredness, stress, anxiety, depression and preexisting agoraphobia without panic disorder.The cause of panic disorder is clearly a complex interaction between constitutional and external factors. This is true of most psychiatric illnesses. Panic disorder is unique in that patients vividly recall their first panic, offering investigators the opportunity to uravel some of these interactions.
Lelliott P. Suicidal Behavior and Onset of Panic Disorder-Reply. Arch Gen Psychiatry. 1991;48(7):669. doi:10.1001/archpsyc.1991.01810310087019