Is delusional disorder a mental illness?

Generally speaking, delusional disorder falls within the category of mental illness and is a type of psychotic disorder, although it differs from the commonly perceived image of severe mental illness characterized by chaos and loss of control. The details are as follows:

Mental illness is not a single disease but rather an umbrella term encompassing various conditions characterized by abnormalities in perception, thinking, and behavior. The core symptom of delusional disorder is persistent and unfounded delusions—such as delusions of persecution or referential thinking—that patients firmly believe despite lack of evidence, and which cannot be easily corrected through reasoning. These distorted thought patterns align with the core features of psychotic symptoms, thus classifying delusional disorder under psychotic disorders.

Unlike severe mental illnesses such as schizophrenia, individuals with delusional disorder typically do not exhibit prominent hallucinations or disorganized thinking. In some cases, their cognitive functions, emotional responses, and social functioning remain relatively intact. This limited presentation often makes early detection difficult; many patients are only recognized when their delusions lead to interpersonal conflicts or other noticeable problems.

In daily life, if someone close to you persistently holds bizarre beliefs that interfere with normal functioning, it is important to encourage them to undergo a professional evaluation. Timely intervention—including psychotherapy combined with medication—can help alleviate symptoms. With appropriate treatment, most patients can maintain basic daily functioning and reduce the impact of delusions on themselves and others.