Illustration of schizophrenia. Schizophrenia is a general term for a group of psycotic illnesses characterised by disturbances in thinking, emotional reaction and behaviour. Schizophrenia is usually described as a 'split personality' because the thoughts and the behaviour of the person affected do not relate in a logical fashion. Disordered thinking is reflected in muddled and disjointed speech. In some cases speech disintegrates and becomes a mixture of odd phrases and detached syllabes.