Physiotherapy can improve the health of people with serious mental illness (SMI) but many are inactive. Adopting theoretically-based evidence considering the motivational processes linked to the adoption and maintenance of an active lifestyle can assist physiotherapists in facilitating lifestyle changes in people with SMI.

Within the Self-Determination Theory (SDT) and the Trans-Theoretical Model (TTM) (stages of change) frameworks, we investigated differences in motives for physical activity between different diagnostic SMI groups.

All participants with SMI from 15 different centers completed the Behavioral Regulation in Exercise Questionnaire 2 (BREQ-2), the International Physical Activity Questionnaire (IPAQ) and the Patient-centered Assessment and Counseling for Exercise (PACE) questionnaire.

Overall 294 persons with SMI (190♀) (43.6±13.6years) agreed to participate. People with affective disorders had higher levels of introjected regulations than people with schizophrenia. No significant differences were found for other motivational regulations. Moreover, no significant differences were found according to gender, setting and educational level. Multivariate analyses showed significantly higher levels of amotivation and external regulations and lower levels of identified and intrinsic regulations in the earlier stages of change. Strongest correlations with the IPAQ were found for motivational regulations towards walking.

Our results suggest that in all people with SMI the level of identified and intrinsic motivation may play an important role in the adoption and maintenance of health promoting behaviours.

The study provides a platform for future research to investigate the relationships between autonomy support, motivational regulations and physical and mental health variables within physiotherapy interventions for this population.