Assessment of schizophrenia and related psychoses

As in the general population, psychoses in people with developmental disability are characterised by loss of touch with reality, delusions and hallucinations. Additional observable features that may manifest in people with developmental disability are outlined in Observable features that may indicate psychoses in a person with developmental disability.

Evaluate symptoms in the context of the person’s developmental stage and premorbid beliefs. While it may be appropriate at some developmental stages to enjoy imaginary friends or fantasy themes, this may complicate presentation of delusions and hallucinations. Changes in the intensity, preoccupation or acting out of pre-existing ideas may indicate psychiatric disorder.

Schizophrenia itself can be associated with cognitive impairments, particularly in executive function (eg attention, working memory and learning, abstract ability, flexibility in thinking, inhibition, planning and organisation). For people with developmental disability who may have pre-existing impairments, this may further exacerbate their deficits.

Common developmental syndromes associated with psychotic illness include autism spectrum disorder, Prader–Willi syndrome and 22q11.2 deletion syndrome.

For more detailed information about psychoses including schizophrenia, see the Psychotropic guidelines.

Table 1. Observable features that may indicate psychoses in a person with developmental disability
Core symptoms	Observable features
delusions	may be more simple in theme and content than in the general population may be an intensification of premorbid beliefs, which has now become a constant preoccupation or unshakeable may have irritability or poor concentration due to focus on delusions or hallucinations
hallucinations	may be able to self-report experience, or it may be observed (eg the person staring at or talking to unseen stimuli, acting out in response to apparent internal stimuli) may be difficult to differentiate from premorbid baseline self-talk—consider hallucinations if fearful, angry or panicked responses present, or there are marked changes in usual themes, mood or intensity of self-talk
disorganisation	disorganised behaviour (eg posturing, echolalia, echopraxia, stereotypy, mutism, stupor, agitation). Some of these may be evident premorbidly thus a baseline history is important in assessing the difference disorganised speech (can manifest as formal thought disorder, derailment, tangentiality, flight of ideas, incoherence)—may be difficult to distinguish from communication difficulties. A baseline of premorbid language and conversational skills from caregivers is useful to determine change in ability. Thought disorder is not a core feature of developmental disability
negative symptoms	amotivation, social withdrawal, disturbance of affect (eg may become odd, fatuous, intense)
functional change	regression in skills and function avoidance or refusal of usual activities intense preoccupation aggression