OBJECTIVES: Obsessive-compulsive disorder (OCD) has been connected to various psychosocial factors that might influence its onset and course. Developmental factors, such as parenting styles or early adverse experiences, and adult attachment have been listed as examples. However, the research on the interconnections of these factors brought mixed results. The study explores the relationship between demographic, clinical, and selected psychosocial factors and the severity of adult OCD. METHOD: Eighty-seven pharmacoresistant inpatients with OCD were admitted between October 2019 and August 2022 for a 6-week cognitive behavioural therapy inpatient program in the psychotherapeutic department. The participants completed the following scales at the start of the hospitalisation: the self-report Yale-Brown Obsessive-Compulsive Scale (Y-BOCS-SR), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI-II), Dissociative Experiences Scale (DES), Childhood Trauma Questionnaire-Short Form (CTQ-SF), PBI (Parental Bonding Instrument), ECR-R (Experiences in Close Relationships - Revised), and a demographic questionnaire. A skilled psychologist administered Mini International Neuropsychiatric Interview (MINI) to confirm the OCD diagnosis and Hamilton Anxiety Rating Scale (HAMA). RESULTS: OCD patients with more severe adverse childhood experiences (ACEs) showed earlier onset of the disorder and more pronounced attachment anxiety, depressive symptoms, and dissociation and subjectively rated the severity of the disorder as more severe. Physical abuse and physical neglect were related to the severity of specific OCD symptoms. Maternal care negatively correlates with clinician-rated anxiety, patient-rated depressive symptoms, and dissociation. The maternal and paternal control positively correlated with patient-rated anxiety and depression. Attachment anxiety negatively correlated with the age of onset and positively with the severity of the clinician-rated anxiety and the patient-rated anxiety, depressive symptoms, and dissociation. CONCLUSIONS: Early adverse experiences, perceived parental styles, and adult attachment anxiety could play a significant role in the symptoms of anxiety, depression, and dissociation. The connection with the specific obsessive-compulsive symptoms is less apparent. Still, adverse childhood events and adult attachment anxiety seem to influence the age of OCD onset.