As noted before, the close temporal association between psychi-atric symptoms and a medical condition does not always reflect PFAMC. If the two are considered merely coincidental, then sep-arate psychiatric and medical diagnoses should be made. In some cases of coincident psychiatric and medical illness, the mental symptoms are actually the result of the medical condition (i.e., the causality is in a direction opposite from that of PFAMC). When a medical condition is judged to be pathophysiologically causing the mental disorder (e.g., hypothyroidism causing depression), the correct diagnosis is the appropriate mental disorder due to a general medical condition (e.g., mood disorder due to hypothy-roidism, with depressive features). In PFAMC, the psychological or behavioral factors are judged to precipitate or aggravate the medical condition.
Substance use disorders may adversely affect many medical conditions, and this can be described through PFAMC. However, in some patients, all of the psychiatric and medical symptoms are direct consequences of substance abuse, and it is usually parsimonious to use just the substance use disorder diag-nosis. For example, a patient with delirium tremens after alcohol withdrawal would receive a diagnosis of alcohol withdrawal de-lirium, not PFAMC, but a patient with alcohol dependence who repeatedly missed hemodialysis treatments because of intoxica-tion would receive diagnoses of alcohol dependence and PFAMC (mental disorder affecting end stage renal disease).
Patients with somatoform disorders (e.g., somatization disorder, hypochondriasis) present with physical complaints which may mimic a medical illness, but the somatic symptoms are actually accounted for by the psychiatric disorder. In prin-ciple, it might seem that somatoform disorders are easily distin-guished from PFAMC, because PFAMC requires the presence of a diagnosable medical condition. The distinction in practice is sometimes difficult because the patient may have both a somato-form disorder and one or more medical disorders. For example, a patient with seizures regularly precipitated by emotional stress might have true epilepsy aggravated by stress (PFAMC), pseudo-seizures (conversion disorder), or both.