Flat affect is having a lack of emotional expression. It is a symptom typically observed in people with schizophrenia, autism, depression or traumatic brain injury. A person with flat affect may appear unresponsive to the world around them.

The psychology term “affect” refers to one’s expression of emotion as demonstrated through facial expression, tone of voice or body language. It represents the degree to which our outer emotional expressions match how we are feeling on the inside. Less severe versions of flat affect are restricted affect (reduced emotional expression) and blunted affect (severity is somewhere between restricted and flat).

Flat affect is different from apathy (lack of emotion) in that feelings may simply be unexpressed rather than totally lacking. For example, a person with flat affect may feel anxious or surprised, but will not express these emotions through facial expressions, tone of voice or body language. This is supported by the ongoing theory that flat affect is the result of a brain abnormality involving motor function rather than emotional processing.

In schizophrenia, flat affect is considered a negative symptom (indicating a lack of something) and is a strong determinant of a patient’s treatment outcome — those with flat affect often fare more poorly than those without flat affect. Research has shown that flat affect is more common in men than women.

One study found that when schizophrenia patients with flat affect are speaking, they are less fluent and use less inflection. These patients also used fewer words and spoke in smaller sentences. Another study found that schizophrenia patients with flat affect have reduced activation in the limbic system when viewing emotional stimuli.

Example: George, who suffered a severe traumatic brain injury a month ago, is starting to heal in many ways but still exhibits flat affect.