Alexithymia is the most common medical term for the symptom or condition of not being able to identify, fully express, or process one’s own emotions or those of others. While alexithymia can be a singular diagnosis, researchers have not yet definitively classified it. Experts have variously considered it a symptom that occurs in tandem with other diagnoses, a standalone disorder, or, sometimes, a simple personality difference between individuals. Symptoms of alexithymia vary but typically include difficulty processing and understanding emotion, overly logical thought patterns, and difficulty understanding bodily reactions, particularly when caused by emotion.

Alexithymia is often comorbid with other diagnoses, particularly neurodevelopmental ones. Some estimate that at least 50% of people with autism have alexithymia. Other diagnoses, such as PTSD or brain injuries, can also be comorbid with alexithymia; in most cases, it is not known how the varying diagnoses affect one another. Anorexia nervosa and other eating disorders are extremely common in individuals with alexithymia, possibly because of the difficulty to internal regulate or understand their own emotions. Additionally, depression and anxiety are extremely common comorbid diagnoses; as with other diagnoses, it is unclear whether alexithymia causes these disorders, is caused by them, or is a mixture of the two.