The overall purpose of the first study (Study 1) is to describe the epidemiology of Alopecia areata (AA) and to assess the current level of primary care service utilisation and management patterns associated with patients diagnosed with AA.~The overall purpose of the second study (study 2) is to assess the prevalence and incidence of mental health conditions (depressive episodes, recurrent depressive disorder and anxiety disorder) in adult patients diagnosed with AA relative to a control population of patients without a diagnosis of AA. In addition, the study will determine both the treatment, 'sick day' and unemployment burden. Treatment burden comprises that of medications and psychological interventions used to treat mental health conditions in adult patients diagnosed with Alopecia areata.~The overall purpose of the third study (Study 3) is to assess the prevalence and incidence of atopic and autoimmune conditions in adult patients diagnosed with AA relative to a control population of patients without AA.~The overall purpose of the fourth study (Study 4) is to assess the incidence of common infections in adult patients diagnosed with AA relative to a control population of patients without AA.
This study series consists of four related studies and aims to explore and describe many important elements of alopecia areata over three key areas: (1) the current epidemiology of alopecia areata, (2) the prevalence and incidence of psychiatric co-morbidities in people with alopecia areata, (3) the prevalence and incidence of autoimmune and atopic conditions in people with alopecia areata, and (4) the incidence of common infections in people with alopecia areata.