The association between visual hallucinations and secondary psychosis: A systematic review and meta-analysis

BackgroundVisual hallucinations are often considered by clinicians to be suggestive of a secondary cause of psychosis, however, this association has never been assessed meta-analytically. We aimed to compare the presence of visual hallucinations in patients with psychosis due to a primary or secondary cause. MethodA meta-analysis of case-control studies directly comparing primary and secondary psychosis was conducted. PubMed, OVID, MEDLINE, Embase, PsychINFO and Global Health databases were searched without date restrictions. Two researchers performed the search independently. The inclusion criteria were studies that reported the frequency of visual hallucinations in patients with primary and secondary psychosis and were published in English. A random-effects model, following the DerSimonian and Laird method, was used to pool studies and generate overall odds ratios (OR) and 95% confidence intervals (CI). ResultsFourteen studies (904 primary and 804 secondary psychosis patients) were included. Visual hallucinations were significantly associated with secondary psychosis (OR = 3.0, 95% CI = 1.7-5.1, p<0.001) with moderate between-study heterogeneity (I2=70%). Subgroup analysis by type of secondary psychosis (organic, drug-induced, mixed) was non-significant. Analysis of the content of visual hallucinations (51 primary and 142 secondary psychosis patients) found hallucinations of inanimate objects more likely to be associated with secondary psychosis (OR = 0.1, 95% CI = 0.01-0.8, p=0.03). ConclusionsVisual hallucinations were found to be strongly associated with a secondary cause of psychosis. The presence of visual hallucinations in a patient presenting with psychosis may serve as a potential red flag for a secondary cause and warrant further investigation. Key messagesO_ST_ABSWhat is already knownC_ST_ABSPsychotic symptoms may arise due to either an idiopathic primary ( non-organic) disorder or a secondary cause, such as an underlying medical ( organic) disorder. Whilst it is widely accepted amongst clinicians that visual hallucinations are associated with a secondary psychosis, this has never been established meta analytically. What this study addsPatients with a secondary cause of psychosis are approximately three times more likely to experience visual hallucinations than patients with a primary psychiatric disorder. The content of visual hallucinations in patients with a secondary cause also differs compared to patient with a primary cause. How this study might affect practiceFindings provide the strongest evidence to date for routinely assessing patients for the presence of visual hallucinations as part of the standard psychiatric assessment. A positive finding should be considered a red flag for a secondary cause.