When talking about schizoid and schizotypal personality disorders, it is important to distinguish them from the class of disorders that share the same root: schizophrenia spectrum disorders. Schizophrenia spectrum disorder is defined by the DSM V as a class of psychotic disorders that range from delusional disorder, brief psychotic disorder, schizophreniform disorder, schizophrenia, schizoaffective disorders, as well as some other less commonly known subsets of psychotic disorders. A couple of key features that define this spectrum are delusions, hallucinations, disorganized thinking and speech, disorganized motor behavior, and diminished emotional expression.
The main differences between these psychotic disorders are usually the varying durations of the key symptoms. Brief psychotic disorder displays the symptoms for at least a day but for less than a month. Schizophreniform disorder stretches that duration for over a month but less than six months, and anything displayed in duration longer than 6 months can be diagnosed definitively as schizophrenia. However, other disorders such as schizoaffective disorder, highlight the presence of mood affective symptoms such as depression and bipolar in concurrence with psychotic symptoms. (American Psychological Association, 2013)
Oddly enough, schizotypal PD falls into this spectrum while schizoid PD does not, even when both require an absence of persistent psychotic symptoms. There seems to be a consensus that schizotypal personality disorder should be seen as a precursor of schizophrenia – instead of being seen as an independent personality disorder.
The differential diagnostic basis for personality disorders and schizophrenia spectrum disorders usually lies in the persistent patterns of thinking and behavior. The DSM V stresses that if the personality traits are not prevalent before the onset and during the remission of psychotic symptoms, the personality disorders should not be diagnosed.
There is much debate on how effectively the current edition of the DSM defines different mental disorders, as there are both merits and disadvantages. The broadness of the schizophrenia spectrum allows people who experience psychosis and related traits to be diagnosed, but the boundaries between each illness and their relationship to schizoid and schizotypal personality disorders remain unclear, and hopefully subject to revision.
References:
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). doi:10.1176/appi.books.9780890423349
