There is considerable evidence that people with psychosis are more likely than people without psychosis to make decisions based on less evidence. This has been termed the 'jumping to conclusions' bias, and several authors have suggested it may be specifically related to the formation and maintenance of delusions. We have conducted several studies to determine the extent to which people with psychosis display this bias, whether it is specifically linked to delusions, and what may cause it:

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Dudley, Taylor, Wickham & Hutton (2015)

 

• We did a systematic review and meta-analysis of 55 studies, which confirmed that people with psychosis more likely to form conclusions based on limited evidence (i.e., jump to conclusions) than people with non-psychotic mental health problems or healthy individuals. The size of the difference was moderate, and it is not notable that a large percentage of healthy individuals and people without psychosis also display the same decision-making bias.

• We also found that the specificity of this bias to delusions was relatively weak, suggesting the bias may be related to psychosis more generally than the specific symptom of delusions.

• The paper is available here

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Croft & Hutton, (in prep)

 

• We conducted a cross-sectional study of the general population (N=160) and found that 'social defeat' accounted for 25% of variance in subclinical psychotic experiences, as predicted by recent theories.

• However we found no evidence that social defeat contributed to sub-clinical psychotic experiences via an increase in the jumping to conclusions bias, suggesting that social defeat and the jumping to conclusions bias are independent causal factors for psychotic symptoms.

 

Galani & Hutton (in prep)

 

• We conducted an experimental study with healthy adults (N=44), and found that temporary induction of worry in these individuals caused an increase in the jumping to conclusions reasoning bias.

• However the temporary increase in worry did not appear to account for the change in reasoning we observed.

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Harris & Hutton (in prep)

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• We conducted another experimental study with healthy adults (N=74), and found that temporary induction of paranoia caused an increase in both paranoia and the jumping to conclusions bias.

• However, as with worry, the effect of the paranoia induction on the reasoning of participants did not appear to occur via increased paranoia.

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We have since conducted several studies to examine whether the jumping to conclusions bias may affect the capacity of people with psychosis to make decisions about their care. This bias is easily modifiable through therapy, so if it is related to capacity, then we may be able to develop ways to support capacity.