Differentiating types of psychosis

Note: my example of a non-bizarre delusion can also be classified as an idea of reference (in which you think that TV or songs are talking about you)

Many psychiatric and general medical conditions can have symptoms of psychosis and mood disorders. The way to figure them out is to look at the timeline and the onset of the psychotic vs. mood symptoms (which came first, are they always at the same time, was there something else going on)

Disorder Duration Psychotic Symptoms Mood Disorder
Schizophrenia More than 1 month of symptoms, disturbance persisting for more than 6 months Present (delusions, hallucinations) Brief duration of mood symptoms
Schizoaffective Disorder Same as schizophrenia Present all along (with and in the absence of a mood disorder) Brief and only at time of psychotic symptoms
Mood Disorder with Psychotic Features Meeting the criteria for depression or bipolar I/II Only at time of mood disorder Present in the absence of psychotic symptoms
Schizophreniform Disorder More than 1 month of symptoms, disturbance persisting less than 6 months Present Brief duration of mood symptoms
Substance-Induced Psychosis During or within 1 month of intoxication or withdrawal (longer implies underlying psychotic disorder) Prominent hallucinations or delusions May exist concurrently
Delusional Disorder At least 1 month Non-bizarre delusions (has never met criterion A in DSM for schizophrenia) Brief in relation to the duration of delusional period

*Brief psychotic disorder: symptoms more than 1 day, less than 1 month and not better accounted for by another psychotic disorder

Dopamine Pathways in the Brain (and schizophrenia)

There are 4 main dopamine pathways in the brain:

  1. Nigro-Striatal: substantial nigra to basal ganglia, involved in movement (what gets affected to cause EPS: tardive dyskinesia, akatisia)
  2. Meso-Limbic: VTA to nucleus accumbens, “reward” pathway (causes the positive symptoms of schizophrenia)
  3. Meso-Cortical: VTA to cortex, motivation and emotional response (thought to cause the negative symptoms of schizophrenia)
  4. Tubulo-Infundibular: hypothalamus to posterior pituitary (hypoprolactinemia in untreated individuals, but D2 blockade with antipsychotics can cause a hyperprolactenemia)


Antipsychotic medication can be divided into 2 classes

  1. Typical/First Generation
  2. Atypical/Second Generation

Typicals are characterized by strong D2 antagonism in the mess-limbic and meso-cortical pathways. This can also lead to significant extrapyramidal symptoms (EPS). They also have strong CYP-450 metabolism (which means lots of interactions with other drugs and grapefruits).

  • High-potency typicals: only slightly anticholinergic & minimally sedating but have more weight gain and a higher risk of EPS
  • Low-potency typicals: more quite sedating and more anticholinergic (bradycardia, GI upset) but have a lower risk of EPS

Atypicals have less risk for EPS, but carry a higher risk for metabolic side-effects and weight gain. While they bind to D2 receptors (like typicals), atypicals have higher affinity for serotonin (5HT) receptors.

Clozapine is a little different from the other atypicals in that is has been shown to have a shorter half-life, which is thought to be why it doesn’t produce as many EPS. However it has the very specific (and serious) risk of agranulocytosis.