Schizotypal personality disorder (STPD or SPD), also known as schizotypal disorder, is a mental and behavioural disorder. DSM classification describes the disorder specifically as a personality disorder characterized by thought disorder, paranoia, a characteristic form of social anxiety, derealization, transient psychosis, and unconventional beliefs. People with this disorder feel pronounced discomfort in forming and maintaining social connections with other people, primarily due to the belief that other people harbour negative thoughts and views about them. Peculiar speech mannerisms and socially unexpected modes of dress are also characteristic. Schizotypal people may react oddly in conversations, not respond, or talk to themselves. They frequently interpret situations as being strange or having unusual meaning for them; paranormal and superstitious beliefs are common. Schizotypal people usually disagree with the suggestion their thoughts and behaviour are a disorder, and seek medical attention for depression or anxiety instead. Schizotypal personality disorder occurs in approximately 3% of the general population and is more commonly diagnosed in males.The term "schizotype" was first coined by Sandor Rado in 1956 as an abbreviation of "schizophrenic phenotype". STPD is classified as a cluster A personality disorder, also known as the "odd or eccentric" cluster. Causes
Genetic
Schizotypal personality disorder is widely understood to be a "schizophrenia spectrum" disorder. Rates of schizotypal personality disorder are much higher in relatives of individuals with schizophrenia than in the relatives of people with other mental illnesses or in people without mental illness.
"At least five of the following symptoms must be present:

ideas of reference
strange beliefs or magical thinking that influences behavior and is inconsistent with subcultural norms (e.g., superstitiousness, belief in clairvoyance, telepathy, or “sixth sense”, bizarre fantasies or preoccupations)
abnormal perceptual experiences, including bodily illusions
strange thinking and speech (e.g., vague, circumstantial, metaphorical, overelaborate, or stereotyped)
suspiciousness or paranoid ideation
inappropriate or constricted affect
strange behavior or appearance
lack of close friends
excessive social anxiety that does not diminish with familiarity and tends to be associated with paranoid fears rather than negative judgments about selfThese symptoms must not occur only during the course of a disorder with similar symptoms (such as schizophrenia or autism spectrum disorder). STPD as a Clinical Disorder
ICD-10
The World Health Organizations ICD-10 uses the name schizotypal disorder (F21). It is classified as a clinical disorder associated with schizophrenia, rather than a personality disorder as in DSM-5.The ICD definition is:

A disorder characterized by eccentric behavior and anomalies of thinking and affect which resemble those seen in schizophrenia, though no definite and characteristic schizophrenic anomalies have occurred at any stage.