Regarding causation, there have been several completely unverifiable ideas. The Freudian school attributed paranoia to repressed homosexuality and fixation at the narcissistic level. Meyer invoked a long-standing personality disorder, the paranoid constitution, using the term to refer to a lifelong tendency to hold biased views, to be overly concerned about what others think of the individual, and to attribute deliberate intentions to indifferent actions. Manschreck presented a detailed discussion of the proposed psychologic mechanisms of paranoia.
The authors’ experience with pure paranoia in a general hospital has been rather limited. One sees deluded patients, to be sure, but usually their abnormal ideas have centered on self-persecution, health and bodily functions, infidelity of a spouse, theft of possessions, and the like. The claim that poisoning by carbon monoxide has left the person with ill-defined defects in concentration and other mental functions or the belief that there exists an unobservable parasitic skin infestation have been the most common delusions in our experience. Whether unshakable beliefs about Lyme disease or environmental toxins or multiple imagined allergies fit in this category is unclear, but the decades-long focus and preoccupation with these and similar themes in some persons makes it likely they have this disorder. One of our patients, functioning normally in every other way, carried the unshakable idea that people were sneaking into her house at night when she was away and rearranging the furniture. She functioned extremely well through her eighties but had a schizophrenic sister. Also, several physicians under our care have woven extensive delusional ideas around tenuous scientific theories; these ideas have applied to personal life events as well as physical and psychologic symptoms and in some cases have resulted in bizarre regimens of self-medication. Rarely, a patient comes to the hospital for some other medical reason and it is found that he or she has been living quietly in the community, preoccupied with a bizarre delusional system yet appearing neither depressed nor schizophrenic. Certainly one often sees delusions in depressed patients who decompensate as their depression deepens.
Sharply separated from the more or less pure delusional disorders are the ones that occur as part of a confusional state or delirium. Delusions occurring in the latter setting are characteristically bizarre, changeable, poorly systematized, and, with rare exceptions, transitory and are associated with many other aberrations of mental function. The same can be said for delusions that occur in the early stages of a dementing disease. Such events are common, of course, in elderly persons with an incipient or well-compensated dementia (“beclouded dementia”; see Chap. 19). Rarely, one of the degenerative dementing diseases of middle and late life (Alzheimer, Huntington, and especially Lewy-body) presents with a delusional disorder. Otherwise healthy persons without known mental illness may experience a brief delusional episode, notably after surgical procedure or the administration of sedative drugs. In most, there are no subsequent mental problems, but a proportion of these older patients will be found to later develop dementia. There is also the frequent problem of varied delusions with manic states that are part of the bipolar disorder discussed in Chap. 48. Here the ideas tend not to be always so clearly persecutory, are usually multiple and disconnected to each other, and often reflect misidentification or distortion of memories.
Certain drugs have a tendency to produce paranoia in otherwise nonpsychotic individuals; corticosteroids, phencyclidine, amphetamine, and cocaine are the main offenders seen in patients arriving in emergency departments, and anticholinergic drugs are often responsible in hospitalized patients. These “organic delusions” have been discussed by Cummings. We also have experience with a few patients who became profoundly depressed after use of interferon for multiple sclerosis and displaced some delusional thinking.