**Background:** Mental ill health is a major public health concern, yet research is often limited by inadequate data availability, transparency, and usability. While mental health is commonly assessed via questionnaires (self-reported or clinician-rated) that capture deep phenotypic information, and increasingly via routinely collected healthcare data that provide population-scale, longitudinal information, the combination of detailed survey data, genetic data, and comprehensive electronic health records is rare. The Scottish Health Research Register Mental Health (SHARE-MH) cohort was established to address this gap by creating a linkable dataset that integrates mental health survey responses, genetic data derived from blood sample diversion, and routinely collected national health records (secondary care, prescribing, death records). The cohort aims to enable research on genetic and environmental determinants of mental health, healthcare journeys, and concordance between self-reported and clinically derived outcomes.
**Methods:** The cohort was formed from 9,829 individuals recruited from the Scottish Health Research Register (SHARE), a voluntary register of individuals over 16 years living in Scotland who consent to be contacted for research and to the use of their electronic health records and spare blood samples for genetic analysis. Between 5 February 2021 and 27 November 2021, SHARE members with valid email addresses (N=179,000) were invited to complete an online mental health survey. The survey included detailed questionnaires covering self-reported diagnoses, depression, suicide, psychosis, anxiety, substance use, adulthood and childhood trauma, serious life events, stress, PTSD, impact of mental ill health, personality, and well-being. Standardized instruments included the Composite International Diagnostic Interview-Short Form, Mood Disorder Questionnaire, Alcohol Use Disorders Identification Test, Childhood Trauma Screener-5, PTSD Checklist-S, Work and Social Adjustment Scale, and Eysenck Personality Questionnaire-Revised. Survey responses were linked to genetic data (Illumina Global Screening Array) and routinely collected health records using a single patient identifier (Community Health Index number) via the Health Informatics Centre (HIC) at the University of Dundee, which operates as a Trusted Third Party. Linked health records included outpatient (SMR00; from 1996), general/acute inpatient (SMR01; from 1981), and mental health inpatient (SMR04; from 1981) admissions, community prescribing (Prescribing Information System; from 2009), and death records. Demographic data were available from both the survey and health records, including age, gender, ethnicity, relationship status, sexual orientation, disability, education, employment, smoking, alcohol use, and area-level deprivation (Scottish Index of Multiple Deprivation, SIMD).
**Key Results:** The cohort comprised 9,829 participants (mean age 57.16 years, SD 14.03; 63% female; 97% White). Compared to the Scottish population, the cohort over-represented females, older adults (32% aged 65-79 vs. 15% in Scotland), retired individuals (38% vs. 15%), and those with degree-level education (56% vs. 26%). Participants were more likely to be from less deprived areas (SIMD decile 10: 17.4% vs. 10.3% in Scotland). Over 40% self-reported a mental health diagnosis (57% reported none), with depression (29%) and anxiety (27%) being most common. 52% had sought or received professional help, and 13% reported self-harm. 74% reported no disability. Linkage to health records was achieved for nearly all participants: 99% had outpatient records (332,713 records), 86% had general inpatient records (65,787 records), 2% had mental health inpatient records (769 records), 99% had community prescribing records (1,869,736 records), and 1% had death records (143 records). The most frequent outpatient specialties were trauma and orthopaedic surgery (8.7%), dermatology (7.9%), and ophthalmology (7.5%). General psychiatry admissions made up 5.0% of outpatient records. Among mental health inpatient admissions, the most common diagnoses were unspecified single episode major depressive disorder (14.9%), emotionally unstable personality disorder (13.5%), and unspecified bipolar disorder (6.2%). Community prescribing records were dominated by cardiovascular system drugs (22.7%), central nervous system drugs (21.0%), and endocrine system drugs (11.5%). Notably, 50% of participants had been prescribed an antidepressant, much higher than the Scottish population (~18%). At the time of writing, 318 participants had genetic data available, with numbers expected to rise as blood sample diversion expands.
**Clinical Implications:** The SHARE-MH cohort provides a unique, linkable resource that enables triangulation of mental health measures across self-reported, genetic, and clinical data sources. The high prevalence of self-reported mental health diagnoses and antidepressant prescribing suggests enrichment for mental ill health, which may benefit psychiatric genetic studies and investigations of treatment trajectories. The cohort allows researchers to examine alignment between subjective treatment experiences and actual healthcare interactions, benchmark data-driven phenotypes, and identify genetic subgroups related to treatment response or resistance. The inclusion of detailed measures of substance use, trauma, and well-being, alongside comprehensive health records, facilitates studies of mental-physical comorbidity and psychosocial determinants. Limitations include potential selection bias (over-representation of females, older adults, and those from less deprived areas) and enrichment for mental ill health, which may limit generalizability but enhance power for certain research questions. Future plans include expanding genetic data, linking to primary care records, and incorporating census, education, and environmental data to broaden the scope of research.