The causes of mental illness are multi-factored with both genetic and environmental elements. Due to social inefficiency some individuals appear to fall down the social scale and classically are overrepresented among the homeless and other socially excluded groups. There is much research about causation but little is as definitive as in other fields of medical practice. We still struggle to understand why some people suffer while others do not. Most research has been driven by observation of empirical improvements in patients after casual treatment which was administered for another reason. Drug research is aimed at identifying treatments using similar molecules to achieve better results. Research has also demonstrated that for many patients institutional care has been negative and so today the tendency is to maintain patients in the community rather than hospital. Patients with mental illnesses are well looked after with modern treatments and knowledgeable staff. There are currently problems in dealing with acute crises and, in particular, ensuring rapid assessment with possible hospital diversion. It is felt that many patients are admitted for conditions which could have been treated with enhanced community services. Overall, there has been emphasis on developing community services and the trained staff resources have been drawn from in-patient services. In the shortterm this transfer of personnel has resulted in a mismatch between supply and demand. It is felt that better early intervention could maintain greater numbers within the community but to be successful community services would require more options.