Post-traumatic stress disorder
Chronic hallucinatory psychosis
Shared delusional disorder
Sometimes in obsessive–compulsive disorder (OCD)
Dissociative disorders, due to many overlapping symptoms, careful differential diagnosis includes especially dissociative identity disorder. Subtypes
Subtypes of psychosis include:

Postpartum psychosis, occurring shortly after giving birth, primarily associated with maternal bipolar disorder
Monothematic delusions
Myxedematous psychosis
Stimulant psychosis
Tardive psychosis
Shared psychosis (folie à deux)

Cycloid psychosis
Cycloid psychosis is typically an acute, self-limiting form of psychosis with psychotic and mood symptoms that progress from normal to full-blown, usually between a few hours to days, and not related to drug intake or brain injury. While proposed as a distinct entity, clinically separate from schizophrenia and affective disorders, cycloid psychosis is not formally acknowledged by current ICD or DSM criteria. Its unclear place in psychiatric nosology has likely contributed to the limited scientific investigation and literature on the topic. Postpartum psychosis
Postpartum psychosis is a rare yet serious and debilitating form of psychosis. Symptoms range from fluctuating moods and insomnia to mood-incongruent delusions related to the individual or the infant. Women experiencing postpartum psychosis are at increased risk for suicide or infanticide. Many women who experience first-time psychosis from postpartum often have bipolar disorder, meaning they could experience an increase of psychotic episodes even after postpartum. Medical conditions
A very large number of medical conditions can cause psychosis, sometimes called secondary psychosis.
The Kraepelinian dichotomy is made questionable by grey matter abnormalities in bipolar and schizophrenia; schizophrenia is distinguishable from bipolar in that regions of grey matter reduction are generally larger in magnitude, although adjusting for gender differences reduces the difference to the left dorsomedial prefrontal cortex, and right dorsolateral prefrontal cortex.During attentional tasks, first episode psychosis is associated with hypoactivation in the right middle frontal gyrus, a region generally described as encompassing the dorsolateral prefrontal cortex (dlPFC). In congruence with studies on grey matter volume, hypoactivity in the right insula, and right inferior parietal lobe is also reported. During cognitive tasks, hypoactivities in the right insula, dACC, and the left precuneus, as well as reduced deactivations in the right basal ganglia, right thalamus, right inferior frontal and left precentral gyri are observed. These results are highly consistent and replicable possibly except the abnormalities of the right inferior frontal gyrus. Decreased grey matter volume in conjunction with bilateral hypoactivity is observed in anterior insula, dorsal medial frontal cortex, and dorsal ACC. Decreased grey matter volume and bilateral hyperactivity is reported in posterior insula, ventral medial frontal cortex, and ventral ACC. Hallucinations
Studies during acute experiences of hallucinations demonstrate increased activity in primary or secondary sensory cortices. As auditory hallucinations are most common in psychosis, most robust evidence exists for increased activity in the left middle temporal gyrus, left superior temporal gyrus, and left inferior frontal gyrus (i.e. Brocas area).