Feasibility and preliminary outcomes of intensive mindfulness and yoga on prisoners with personality disorders: A randomised controlled preliminary study

This study was the first to test the feasibility of mind-body interventions with a randomised control research design in a sample that contains all ten types of personality disorders, and the first to provide a preliminary evaluation of responses using a combination of psychological, genomic, neural, and behavioural measures. Thirty prisoners with personality disorders were recruited within a clinical unit of a high security prison and assigned to a mindfulness intervention (n=10), a yoga intervention (n=10), or a wait-list control group (n=10). Both mindfulness and yoga interventions were held simultaneously and lasted three hours per day on five consecutive days. At baseline and after the intervention, we measured inflammation-related gene expression through venous blood; attention with a cognitive task; event-related potentials (ERPs) with EEG; and stress, emotion regulation and mindfulness with questionnaires. Here we show that recruitment and dropout rates were satisfactory, and data collection was successful despite its length and complexity. The only exception were blood samples where 60% of participants refused to give blood, but this was expected because 47% of recruited participants had a diagnosis of paranoid personality disorder. Unexpected difficulties occurred when participants did not fully adhere to randomisation procedures, and a riot took place during the final day of the interventions. This study was underpowered to detect changes on primary or secondary outcome measures, but despite that 80% of examined inflammation-related genes showed medium and large effect sizes suggesting this as an important outcome measure in future studies. Minor adjustments to the study design are necessary before a larger scale study can be conducted to precisely determine the effects of mindfulness and yoga as an additional treatment for prisoners with personality disorders.