Cognitive behavioural therapy emphasizes the importance of the role of cognitions and behaviour in the formation and maintenance of psychiatric disorders and emotional problems. Even if there could be said to be various alternative versions of delivering cognitive behavioural therapies, there are some common factors related to treatment principles and cognitive behavioural techniques which integrate these different approaches. A clear distinction was drawn between normality and abnormality, and the causes of a certain number of diagnosable mental illnesses were understood as inherited brain disorders or infections, for example, syphilitic mental disorders. Psychotic symptoms such as mania, delusions and voice-hearing are actually difficult to sort into neat categories as diagnoses, and are best understood on a continuum of symptoms. Delusional beliefs and auditory hallucinations are based upon thoughts and assumptions that the patient believes to be true and real, and they are held with great intensity and often preoccupy the person.