Astrength of such a research strategy is that it facilitates
investigation as to whether there are psychological processes that are specific to the
occurrence of delusions in each disorder. In order to study delusion-specific factors a
closely matched control group of individuals without delusions is needed; it is difficult
to recruit a control group of individuals with schizophrenia who have never had
delusions but the task is simpler for individuals with depression and individuals with
neurological disorder. Furthermore, it is significant for the new model of persecutory
delusions that delusions in mood disorders such as bipolar disorder and depression are
associated with emotion (by diagnostic definition). This is a clear indication of direct
roles for emotion in delusion formation and maintenance.