Psychiatric symptoms in thyroid diseases such as Hashimoto's thyroiditis and Graves' disease, are well known. In particular, patients with autoimmune thyroid disease may develop psychoses that are nonspecific. This is expected because autoimmune thyroid disorders typically cause a disorganization of the nervous system. This neurobiologic disorganization is also a common feature of nonspecific psychoses, including bipolar disorders. Cognitive dysfunction is also a common feature of hypothyroidism and this symptom may confuse diagnoses of psychoses and other psychiatric illnesses.
Schizophrenia and Hypothyroidism
In many ways, the psychiatric symptoms of hypothyroidism resemble the symptoms seen in schizophrenia. However, the confusion seen in acute schizophrenia differs from the psychoses seen in hypothyroidism because the latter condition typically causes cognitive impairment rather than confusion. In schizophrenia, disturbances of memory and orientation are rare although they are common in hypothyroidism.
Symptoms in hypothyroid psychosis, especially those occurring in elderly patients, may closely mimic those seen in the severely psychotic affective states. For this reason, experts suggest that all patients showing psychiatric symptoms be screened for thyroid disease.
Psychiatric Aspects of Hyperthyroidism and Hypothyroidism
The symptoms of hypothyroid psychoses are most pronounced in patients who suddenly move from hyperthyroidism to hypothyroidism, including patients undergoing treatment for hyperthyroidism with radioiodine ablation, excessively high doses of anti-thyroid drugs, and surgery.
Hyperthyroidism itself causes multiple and varied neurobehavioral and psychological changes including anxiety, dysphoria, emotional lability, insomnia, and occasionally episodes of intellectual dysfunction. Concentration may be impaired, and patients may speak rapidly, expressing disjointed thoughts.
Motor activity is often increased and usually associated with agitation. Mania may occur although surprisingly it is rarely seen. Sleep disturbances in hyperthyroidism may cause decreased daytime energy. In mania, increased energy, irritability, and decreased sleep are the most common symptoms.
When true mania and hypomania occur in patients with thyrotoxicosis (effects of hyperthyroidism), the patients typically have a previous diagnosis or a family history of bipolar disorder.
Rarely, the behavioral changes that occur in hyperthyroidism may progress to a nonspecific psychotic illness with bizarre delusional thoughts, usually of a paranoid nature. Here, cognitive clouding suggests that the psychotic changes are directly correlated with this evidence of delirium. In patients with thyroid storm, delirium, restlessness, and agitation can appear acutely.
Diagnostic Problems
Because patients with thyroid disorders have a considerable overlap between mental and physical complaints including loss of energy and tremulousness, the true incidence of psychiatric symptoms in patients with thyroid disorders is hard to estimate. Overall, about 10 percent of patients with hyperthyroidism are suspected of having neuropsychiatric symptoms. In addition about 31 percent of patients have depression, and 62 percent have anxiety disorders. Patients with subclinical hyperthyroidism are also reported to show increased anxiety and irritability and decreased vitality and activity when compared to normal subjects. Panic disorders are rarely seen in hyperthyroidism although they are likely to occur in hypothyroid patients.
Depression is more likely to occur in hypothyroidism. Because of slowing of thought and speech, decreased attentiveness, poor concentration, and diminished interest in and responsiveness to others, the diagnosis of hypothyroidism may be missed and confused with depression. In hypothyroid patients with psychosis, the diagnosis may be confused by symptoms of insomnia, hyperactivity, irritability, anger, and both auditory and visual hallucinations. Patients with hypothyroidism may also become fearful, suspicious, and delusional.
Bipolar Disorder
Thyroid dysfunction is particularly important when evaluating the clinical course of bipolar disorder, especially rapid cycling disease, which is a severe form of this disorder. Patients with rapid cycling disease, which is characterized by four or more bipolar episodes annually, have a much higher incidence (about 25 percent) of subclinical hypothyroidism than depressed patients.
Resources:
Peter Whybrow and Michael Bauer, "Behavioral and Psychiatric Aspects of Hypothyroidism", The Thyroid, A Fundamental and Clinical Text, 8th Edition, edited by Braverman and Utiger, 2000.
Peter Whybrow and Michael Bauer, "Behavioral and Psychiatric Aspects of Thyrotoxicosis", The Thyroid, A Fundamental and Clinical Text, 8th Edition, edited by Braverman and Utiger, 2000.
