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Background Subthalamic Nucleus (STN) is commonly targeted in Deep Brain Stimulation (DBS) in patients with Parkinson’s to treat medication-resistant motor symptoms. 1 This is also considered effective in reducing medication-related side effects, such as impulsive behaviours (ICBs).2 However, the subthalamic nucleus is integral to behaviours’ cognitive, motor, and emotional aspects.3 It is still not established whether STN stimulation could lead to the worsening or development of de novo cases of ICBs and other psychiatric disorders.4 Method The CRISP study is a multicentre observational study recruiting patients with Parkinson’s undergoing DBS at seven participating centres across the UK. Patients will complete a set of self-rated and clinician-rated questionnaires, including QUIP-RS, Parkinson’s Impulse Control Scale (PICs) once before DBS activation, and three times 3, 6, and 12 months after the operation.Objective 1) Does DBS worsen, improve or lead to de novo cases of impulsive behaviours (QUIP-RS)? 2) Does DBS affect other psychiatric symptoms, including mood, apathy, personality traits and carer’s burden?Results 73 (50 male) patients have been recruited, of which 61 have completed the 2nd postop 6-month follow-up. 26% of patients at baseline scored above the cutoff point on QUIP-RS for impulsivity. For individual impulsive behaviours on QUIP-RS, the prevalence at baseline was 32% (n=23) for hobbyism-punding, 17.8% for binge eating (n=13), 16% (n=12) dopamine dysregulation syndrome, 6.8% for hypersexuality (n=5), 5.5% gambling (n=4), 4.1% compulsive shopping (n=3). The prevalence of patients scoring above a clinical cutoff point on respective instruments was high at 53% depression (PHQ-9), 16% anxiety (GAD-7), 29% apathy (AES), 96% carers’ burden (ZBI). At 6 months postop, the impulsivity reduced significantly for total impulsivity score on QUIP-RS, hypersexuality and hobbyism-punding. There were 9 cases of de novo ICBs. As for secondary outcomes, anxiety significantly reduced, depression did not change and apathy significantly worsened. Personality traits remain mainly stable, and carer’s burden reduced. Improvement in the ICD total was predicted at 6-month follow-up by baseline anhedonia. Depression, cognition, and anxiety were worse in de novo cases.Discussion the effects of STN-DBS are generally positive for impulsive behaviours but not equal across sub-types of these behaviours. More data must be collected Among de novo cases to identify contributing factors. As for other psychiatric outcomes, at 6 months, there was an improvement in anxiety, no effect on depression and a worsening in apathy. Other studies have reported this change in apathy, and further attention is needed regarding the pacing of medication reduction and selection/programming of electrode contacts. Furthermore, the role of personality traits in impulsivity in DBS candidates requires further study.Conclusion At 6-month postoperative follow-up, the results are generally positive for the effects of STN-DBS on the psychiatric profile of patients with Parkinson’s, except for apathy. It is unknown whether this will still happen at the 12-month follow-up.References Okun MS. Deep-brain stimulation for parkinson’s disease. New England Journal of Medicine 2012;367(16):1529–1538. https://doi.org/10.1056/NEJMct1208070Voon V, Saint-Cyr J, Lozano AM, Moro E, Poon YY, Lang AE. Psychiatric symptoms in patients with Parkinson disease presenting for deep brain stimulation surgery. Journal of Neurosurgery 2005;103(2):246–251. https://doi.org/10.3171/jns.2005.103.2.0246Theis H, Probst C, Fernagut PO, van Eimeren T. Unlucky punches: the vulnerability-stress model for the development of impulse control disorders in parkinson’s disease. NPJ Parkinson’s Disease 2021;7(1):112. https://doi.org/10.1038/s41531- 021-00253-zPallanti S, Bernardi S, LM R, Marini P, Ammannati F, Sorbi S, Ramat S. Complex repetitive behavior: punding after bilateral subthalamic nucleus stimulation in parkinson’s disease. Parkinsonism & Related Disorders 2010;16(6):376–380. https://doi.org/10.1016/j.parkreldis.2010.02.011