From the time a girl reaches puberty until about the age of 50, she is twice as likely to have an anxiety disorder as a man. Anxiety disorders also occur earlier in women than in men.

Women are also more likely to have multiple psychiatric disorders during their lifetime than men. The most common to co-occur with anxiety is depression.

Differences in brain chemistry may account for at least part of these differences. The brain system involved in the fight-or-flight response is activated more readily in women and stays activated longer than men, partly as a result of the action of estrogen and progesterone.

The neurotransmitter serotonin may also play a role in responsiveness to stress and anxiety. Some evidence suggests that the female brain does not process serotonin as quickly as the male brain. Recent research has found that women are more sensitive to low levels of corticotropin-releasing factor (CRF), a hormone that organizes stress responses in mammals, making them twice as vulnerable as men to stress-related disorders.