This paper presents double unconscious guilt as an aetiological psychological factor in the development of schizophrenia and schizoaffective disorder. Two instances of guilt are caused unconsciously by experiences with an external source, eg. a schizophrenic individual. If these experiences of unconscious guilt are accessed by another external factor they may become conscious, and lead to the experience of schizophrenia or schizoaffective disorder. Other factors in the aetiology of schizophrenia and schizoaffective disorder include a genetic basis, which may affect physiological processes eg. in the prefrontal cortex, relating to dysfunction of pyramidal cells involving NMDA receptors. Sensory misattribution may lead to false inference. This in turn may lead to delusions, a common symptom of schizophrenia. Schizoid illness may run in families: bipolar disorder and schizoaffective disorder occur more commonly in families which have a schizophrenic member. Psychoanalytic psychotherapy in skilled hands may lead to resolution of the psychological symptoms and difficulties experienced by a schizophrenic or schizoaffective patient. Careful prescription of medication and secure inpatient care involving treatments such as group psychotherapy as further treatments may, when carefully supervised, led to resolution of the conditions