This kind of insecurity leads to overcompensation: compulsive formality, strict social observances and exaggerated displays of assurance.In 1950, Kurt Schneider described the "fanatic psychopaths" and divided them into two categories: the combative type that is very insistent about his false notions and actively quarrelsome, and the eccentric type that is passive, secretive, vulnerable to esoteric sects but nonetheless suspicious about others.The descriptions of Leonhard and Sheperd from the sixties describe paranoid people as overvaluing their abilities and attributing their failure to the ill-will of others; they also mention that their interpersonal relations are disturbed and they are in constant conflict with others.In 1975, Polatin described the paranoid personality as rigid, suspicious, watchful, self-centered and selfish, inwardly hypersensitive but emotionally undemonstrative. However, when there is a difference of opinion, the underlying mistrust, authoritarianism and rage burst through.In the 1980s, paranoid personality disorder received little attention, and when it did receive it, the focus was on its 
potential relationship to paranoid schizophrenia. The most significant contribution of this decade comes from Theodore Millon who divided the features of paranoid personality disorder to four categories:1) behavioral characteristics of vigilance, abrasive irritability and counterattack,
2) complaints indicating oversensitivity, social isolation and mistrust,
3) the dynamics of denying personal insecurities, attributing these to others and self-inflation through grandiose fantasies
4) coping style of detesting dependence and hostile distancing of oneself from others. Controversy
Due to repeated concerns of the validity of PPD and poor empirical evidence, it has been suggested that PPD be removed from the DSM.
Paranoid personality disorder (PPD) is a mental illness characterized by paranoid delusions, and a pervasive, long-standing suspiciousness and generalized mistrust of others. People with this personality disorder may be hypersensitive, easily insulted, and habitually relate to the world by vigilant scanning of the environment for clues or suggestions that may validate their fears or biases. They are eager observers. They think they are in danger and look for signs and threats of that danger, potentially not appreciating other interpretations or evidence.They tend to be guarded and suspicious and have quite constricted emotional lives. Their reduced capacity for meaningful emotional involvement and the general pattern of isolated withdrawal often lend a quality of schizoid isolation to their life experience. People with PPD may have a tendency to bear grudges, suspiciousness, tendency to interpret others actions as hostile, persistent tendency to self-reference, or a tenacious sense of personal right. Patients with this disorder can also have significant comorbidity with other personality disorders, such as schizotypal, schizoid, narcissistic, avoidant and borderline. Causes
A genetic contribution to paranoid traits and a possible genetic link between this personality disorder and schizophrenia exist. A large long-term Norwegian twin study found paranoid personality disorder to be modestly heritable and to share a portion of its genetic and environmental risk factors with the other cluster A personality disorders, schizoid and schizotypal.Psychosocial theories implicate projection of negative internal feelings and parental modeling.