Mental and physical complaints in thyroid disorders in the general population
Grabe HJ, Volzke H, Ludemann J, Wolff B, et al.;
Commented by , 23 Oct 2005
Background
Thyroid disorders are thought to be causal factors in mental health disorders such as anxiety and depression. However, most studies have been in medical out-patients with established thyroid disorders, possibly reporting non-causal comorbidity. This study sought to analyze any links between symptoms of mental ill health and thyroid disorder in a community (non-patient) population.
Aims
To test the hypothesis that newly diagnosed overt hypo- and hyperthyroidism are associated with mental and physical complaints in a community sample.
Methods
The study population was part of a wider study in Pomerania, West Germany, comprising 212,100 inhabitants. An age-stratified cluster sampling process resulted in 7,008 people aged 20–79 being invited to a medical examination centre, 4,310 (68.8 %) participated.
Sociodemographic characteristics and history of thyroid disorder were recorded, and a modified version of von Zerssen’s complaints scale used to assess mental and physical symptoms by self report on 38 items. Subjects with a history of thyroid disorder were excluded.
Blood tests were taken for serum thyrotropin (TSH), free thyroxine (FT4), free tri-iodothyronine (FT3) and autoantibodies to thyroperoxidase. Predetermined definitions of clinical and subclinical thyroid under and overactivity were used.
Univariate and multivariate analysis of variance was used to established links between (subclinical) thyroid disorder and physical/mental symptoms.
Results
349 subjects (62 men and 287 women) of 4,310 had known thyroid disorder, a further 20 were excluded because of an uncertain history. 151 other subjects were excluded because of incomplete data or missing blood tests, leaving 3,941 participants.
Overt hyperthyroidism (prevalence 0.4 %) was associated with a significantly lower total complaint score than euthyroid subjects. Subjects with overt hypothyroidism (0.5 %), subclinical hypothyroidism (0.7 %) and subclinical hyperthyroidism (1.6 %) were no different from controls in total or subset complaint scores.
The only subgroup to record more highly on the complaint scale were 45 women with autoimmune thyroiditis, 30 of whom were clinically and biochemically euthyroid. These subjects scored significantly more for anxiety, globus sensation, tachycardia and nausea.
Dr Seymour's comments
The association between physical and mental health symptoms and thyroid disorder has been long established in the medical literature, based usually on secondary care populations and case reports of patients with marked and/or long standing disease.
This community-based study that excluded people with established disease, calls into question any causal link in subjects with milder or subclinical hyper- or hypothyroidism, with the noteworthy exception of women with clinical or subclinical autoimmune thyroiditis.
Indeed, hyperthyroidism was associated with positive overall effects on self-rated mental and physical health.
This is an interesting contribution to the literature. Clearly, the cross-sectional design and limitations of the self-reported rating scale do not allow firm conclusions to be drawn, but it is likely that only well entrenched and untreated thyroid disorder will cause mental disorder.