Overthinking at night - about insomnia and other matters - is a common problem for many of my patients with sleep disorders. It interferes with falling asleep or going back to sleep, and prevents peaceful rest when they can't sleep anyway.
Overthinking usually refers to thought processes such as racing thoughts or perseveration. The content - such as worries or the next day's demands - may also be maladaptive. It may be fueled by a diagnosable condition such as depression, generalized anxiety disorder, obsessive compulsive disorder (OCD), attention deficit/hyperactivity disorder (ADHD), post-traumatic stress disorder (PTSD) or hypomania. It can also be stimulated by intense experiences such as stress, exciting plans, perfectionism, insecurity, caffeine use or a painful or worrisome life event.