Maladaptive daydreaming or excessive daydreaming is a psychological concept first introduced by Eli Somer to describe an extensive fantasy activity that replaces human interaction and/or interferes with academic, interpersonal, or vocational functioning. It might be related to childhood emotional neglect or abuse that motivate victims to divorce from the threatening world and from their material entity. 
Identified functions of maladaptive daydreaming included disengagement from stress and pain by mood enhancement and wish fulfillment fantasies; and companionship, intimacy, and soothing.
While there are many specific symptoms of a maladaptive daydreamer, someone suffering from this disorder will not necessarily suffer from all of them.
Often maladaptive daydreamers will have 'triggers' that set off their daydreams. Common triggers are books, movies, and music. Maladaptive daydreamers also may have trouble getting out of bed or going to sleep, due to the want to contain daydreaming. Oftentimes while maladaptive daydreamers are daydreaming they will whisper, talk, make facial expressions, or do some sort of repetitive movement.
Maladaptive daydreamers can spend hours simply daydreaming. They often have elaborate fantasies within their minds, often comparable to a complete novel or movie. Many have more than one fantasy in their mind, each with its own characters, setting, plots, etc. Maladaptive daydreamers may become emotionally attached to their characters as well, though they know the characters are not real.
Recurrent themes may include:
- Idealized self
- Power and control
- Rescue and escape
- Sexual arousal
- Attention deficit hyperactivity disorder
- Borderline personality disorder
- Dissociative disorder
- Fantasy prone personality
- Video game addiction
- Somer, Eli. "Maladaptive Daydreaming: A Qualitative Inquiry". Journal of Contemporary Psychotherapy. Journal of Contemporary Psychotherapy. Retrieved 18 May 2014.
- Ardino, Vittoria (ed.). Post-Traumatic Syndromes in Childhood and Adolescence. Chichester, West Sussex, UK: Wiley-Blackwell. p. 162. ISBN 978-0-470-66929-7.
- "Maladaptive Daydreaming- What Is It?" -Medical Daily
- The Atlantic featured an article on Maladaptive Daydreaming. "When Daydreaming Replaces Real Life Should elaborate fantasies be considered a psychiatric disorder?" (April 2015)
- CBC Radio's The Current featured an episode on the subject called "Maladaptive daydreaming, a debilitating condition with no escape" (June 2015)
- Living in an Imaginary World. Scientific American (January 2014)