It may have a neurological, psychological or psychosomatic cause. Early theories suggested the irritable bowel was caused by a psychosomatic or mental disorder. This theory can account for several psychophysiological phenomena and psychosomatic illnesses. Medical treatments and psychotherapy are used to treat illnesses believed to have a psychosomatic component. Some researchers suggested that ulcers were a psychosomatic illness. Al-Ghazali and William James rejected their pessimism after suffering psychological, or even psychosomatic illness. Anxiety, depression and psychosomatic symptoms are common among both bullies and their victims. Similarly, high scorers on neuroticism are more susceptible to sleep and psychosomatic disorders. Studies have yielded mixed evidence regarding the impact of psychosomatic factors in illnesses. Psychosomatic and cognitive factors are important in the evaluation of patients with chronic dyspepsia. Dowie appeared to cure a range of psychosomatic illnesses with his stagecraft. Logotherapy has also been associated with psychosomatic and physiological health benefits. James described two opposing views of what causes many ill-defined "psychosomatic" illnesses. Many believe that magic is effective psychologically as it has placebo effect to psychosomatic diseases. It is difficult to establish for certain whether an illness has a psychosomatic component.