Self- and other-agency in people with passivity (first rank) symptoms in schizophrenia.

Individuals with passivity (first-rank) symptoms report that their actions, thoughts and sensations are influenced or controlled by an external (non-self) agent. Passivity symptoms are closely linked to schizophrenia and related disorders yet they remain poorly understood. One dominant framework posits a role for deficits in the sense of agency. An important question is whether deficits in self-agency can be differentiated from other-agency in schizophrenia and passivity symptoms. This study aimed to evaluate self- and other-agency in 51 people with schizophrenia (n=20 current, 10 past, 21 no history of passivity symptoms), and 48 healthy controls. Participants completed the projected hand illusion (PHI) with active and passive movements, as well as immediate and delayed visual feedback. Experiences of agency and loss of agency over the participant's hand and the image ('the other hand') were assessed with a self-report questionnaire. Those with passivity symptoms (current and past) reported less difference in agency between active and passive movements on items assessing agency over their own hand (but not agency over the other hand). Relative to the healthy controls, the current and never groups continued to experience the illusion with delayed visual feedback suggesting impaired timing mechanisms regardless of symptom profile. These findings are consistent with a reduced contribution of proprioceptive predictive cues to agency judgements specific to self representations in people with passivity symptoms, and a subsequent reliance on external visual cues in these judgements. Altogether, these findings emphasise the multifactorial nature of agency and the contribution of multiple impairments to passivity symptoms.