Table 1.

Overview of included papers.

Author Year	Design	Participants, N and characteristics	Criteria included	Equivalents described
Bakken et al. 2007	Qualitative Case reports	N = 8, ASD, Moderate/severe ID, SCZ/psychosis, severely impaired functioning	Disorganized behaviour/speech, Negative symptoms Suggested hallucinations	Disorganization NS Hallucinations
Bakken et al. 2008	Quantitative Staff communication	N = 4 Patients Moderate/severe ID, SCZ/psychosis, severely impaired functioning	Disorganized behaviour Disorganized speech	Disorganized behaviour/speech
Bakken et al. 2009	Single-case design. Validation of behavioural disorganization	N = 84 episodes of dyadic patient – staff interaction	Disorganised behaviour Disorganised speech	Disorganized behaviour/speech
Bakken 2014	Case series. Differing SCZ from ASD	N = 12, Mild ID / Borderline IQ. Tentative ASD and / or SCZ at admission	Delusions Hallucinations Disorganized speech/behaviour Negative symptoms Globally impaired function	Disorganizes speech Disorganized behaviour Negative symptoms
Engebretsen et al. 2019	Clinical study. 22q11.2 DS and psychosis.	N = 1 Patient with mild ID, 22q11.2 DS and psychosis	Hallucinations Disorganized speech Disorganized behaviour Negative symptoms	Disorganized speech Disorganized behaviour Negative symptoms
Hurley 2003	Clinical study; psychosis in adults with ID in two groups.	N = 106 adults with ID. One group with ‘ID only’. One group with ID + Down Syndrome.	Delusions Hallucinations	Disorganized speech? Hallucinations
Kildahl et al. 2017	Clinical study. Assessment of psychosis in ID / ASD	N = 1 Patient with mild ID, ASD and severely impaired global functioning	Disorganized speech Disorganized behaviour Negative symptoms	Disorganized speech Disorganized behaviour Negative symptoms
Rumsey et al. 1986	Group comparisons	N = 56 Four groups of adults; one group ASD, one group SCZ inpatients, one group mania inpatients, one group neurotypicals (no mental problem)	Formal thought disorder (disorganized speech)	Disorganized speech

The first column refers to first author and year published. *NS = negative symptoms.