Anxiety disorders are characterized by inappropriate or excessive activation of the “fight or flight” system, resulting in central nervous system components of fear and worry and peripheral effects reflecting activation of the sympathetic nervous system. For these reasons, anxiety potently disrupts sleep. Anxiety disorders are the most common comorbid conditions found in insomnia patients, occurring in 24% to 36% of individuals diagnosed with insomnia (1,2). Anxiety and insomnia are strongly inter-related. Not only does anxiety contribute to insomnia, but insomnia increases the likelihood of developing a subsequent anxiety disorder compared to individuals without insomnia (14% vs. 7%) (2). Insomnia occurs frequently with generalized anxiety disorder (GAD), but it is much less commonly associated with certain phobias and obsessive compulsive disorder (OCD). Patients with OCD who have a compulsion to repeatedly check doors before going to bed or any other similar compulsion can have significant sleep-onset insomnia (3). Likewise, phobias associated with nighttime, such as phobias regarding the dark, being alone, or those with social phobia the night before a feared social circumstance is scheduled to occur, are more likely to have impaired sleep.