They are types of mental disorders in which a person has a rigid and unhealthy pattern of thinking, functioning, and behaving.
Example- paranoid disorder (distrust & suspicion of others' motives), Schizoid personality disorder(Lack of interest in social or personal relationships, preferring to be alone), etc.
Such disorders are usually difficult to cure.
Medications (antidepressants, anti-anxiety medicines, etc) and psychotherapy may be used to treat them.