While knowledge of the aetiology of psychiatric disorders is complex and has not been fully elucidated, recently it has been noted that a sizeable proportion of psychiatric patients have coexisting immunological health conditions. It is debatable whether inflammatory factors plays a role in the aetiology of the psychiatric conditions, or if psychiatric conditions predispose to immune dysfunction. However, previous work has given weight to the theory that the immune system has important neuromodulatory roles in the brain, and disturbances in this system can lead to psychiatric manifestations. Epidemiological evidence is needed to explore the strength of the correlation between immune conditions and psychiatric disorders, and this audit attempts to investigate this potential association using the psychiatric patient databaseof Bedford East Community Mental Health Team (Bedfordshire, UK). In this audit, the patient information was analysed to obtain prevalence data for an array of autoimmune conditions. This was then compared to the expected prevalence of the same autoimmune conditions. The results showed that patients with each psychiatric condition had a higher than expected prevalence of autoimmune conditions overall. The most striking discrepancy was that the percentage of patients with coexisting hypothyroidism was higher than expected in almost every psychiatric condition recorded. Other patterns in prevalence of autoimmune conditions were also noted. A causative link between psychiatric and autoimmune diseases is still questionable, and this issue needs to be researched further in terms of prevalence data and aetiological evidence. There are significant implications for clinical practice if a greater incidence of autoimmune conditions among psychiatric patients is proven. This includes screening opportunities and risk assessments, as well as potential for new pharmacological therapies based around immune regulation.