Not everyone responds to emotional stimuli in the same way. In some, there may be no response at all. This lack of reaction is called flat affect. It can be a symptom of a psychiatric disorder or a side effect of another medical condition.

Those with flat affect do not lack emotion, but rather their emotions are thought to be unexpressed. This visual or verbal absent can be caused by conditions that include schizophrenia, autism, depression, and traumatic brain injury.

Emotions to stimuli that are not expressed by people with flat affect include facial, voice and body language changes.

Fast facts on flat affect:

  • It is characterized by reduced expression and displays of emotion.
  • It differs from the “thousand yard stare” associated with post traumatic stress disorder and is more likely a sign of an underlying mental illness.
  • In some conditions, including autism and schizophrenia, those affected may not be able to identify the emotional responses of others.
  • When it is a side effect or symptom of a medical condition, flat affect may impact people differently.
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Flat affect is characterized by a lack of response to emotional stimuli. This may include having a neutral facial expression.

Symptoms of flat affect can include:

  • monotone voice
  • lack of eye contact, changes in facial expressions, or interest
  • lack of verbal and nonverbal responses

Typically, a particular experience or situation will produce an emotional response in someone, such as elation, fear, sadness, or anger.

Therapist Deb Smith explains “in those who are experiencing a flat affect, these normal responses are not exhibited. For example, a person without flat affect who is experiencing a happy event will typically exhibit behaviors indicating happiness, such as smiling and laughter, whereas someone with a flat affect will show no response.”

For example, a person who is exhibiting a symptom of flat affect may not be able to empathize with a person who is sad, angry, or happy.

For some people and for some medical conditions, flat affect may be more pronounced than others.


Schizophrenia is a severe form of mental illness where someone has auditory and visual hallucinations, false beliefs, disorganized thought and behavior patterns, and a flat affect.

The flat affect experienced by those with schizophrenia is due to an impairment in the way they function on an emotional level. It is deemed a negative side effect of the disease, as it is not in line with normally expected emotions and behaviors.


Depression is a common mental health condition where a person experiences feelings of sadness, which can lead to a loss of interest in activities, decreased productivity, and other emotional and physical symptoms and conditions.

In some people, this state of mind and body can lead to a person displaying flat affect.


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One of the potential symptoms of autism is flat affect.

Autism is a condition with varying symptoms and severity, but which describes a spectrum of disorders that include abnormal or challenging social skills, repetitive behaviors, and abnormalities in speech and nonverbal communication.

Some of those affected by autism will be unable to speak and intellectually disabled to varying degrees. Consequently, those with autism are often described as having flat affect.

Parkinson’s disease (PD)

Parkinson’s disease is a neurological disease most commonly affecting the older population that presents with symptoms, including resting tremor, rigidity, limited movements, and instability. Some people with PD also experience depression, anxiety, psychosis, dementia, and flat affect.

Traumatic brain injury (TBI)

Those who suffer a traumatic brain injury caused by a blunt trauma, fall, blast injury or other violent situation may experience post-trauma flat affect.

In addition to blunt trauma, brain injuries caused by strokes, especially right hemisphere strokes, can cause a person to experience flat affect.

While flat affect and blunted affect may sometimes appear interchangeable, they are different.

Those with flat affect have no response to emotional stimuli. Blunted affect, however, describes a dulled or constricted response, where a person’s emotional response is not as intense as normally expected.

Blunted affect is commonly seen in those with post-traumatic stress disorder or PTSD.

When an event causes a person to experience or witness physical harm or violence, they can go on to develop PTSD. This may cause them to have long-term anxiety and fear, which can be debilitating.

PTSD has many symptoms and often leads to nightmares and flashbacks to the original event. People with PTSD can also experience social detachment and a blunted or numbed affect in response to emotional stimuli.

Again, trauma therapist Deb Smith explains that “many clients coming in for treatment of PTSD will initially present with a blunted affect. However, the combination of treatments used to treat PTSD often alleviate that symptom. This in turn returns the client to their pre-trauma affect.”

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Therapy and counseling may help by addressing the root cause of flat affect.

Treating flat affect can be challenging, as it depends on the underlying cause. People who think that they or a loved one may be experiencing symptoms of flat or blunted affect should speak to a doctor for evaluation.

Learning more about what could be causing this symptom is vital if a person is to be treated in the most appropriate way.

Therapists, psychologists, and other specialist doctors will be better able to assess and treat a person with flat affect after they have evaluated the individual’s health history and done a physical examination.

Additionally, a careful review of any medications may be helpful in determining the cause of flat affect.