Introduction: It is standard teaching that thyroid function is associated with mood, in particular hypothyroidism with depression. Recent studies however have provided conflicting data, with community based studies suggesting no relationship, but a study in patients on thyroxine showing an association. There may be biases involved in these studies as in communities with good health care, symptomatic people with mildly abnormal thyroid function are often put on thyroxine and excluded from these studies. We overcame this by reanalysing a large community based cohort looking at the association between thyroid function and mood in those 1) with no history of thyroid disease and with serum TSH within the reference range and 2) on thyroxine.
Methods: We analyzed data from the HUNT study on a large sample of community dwelling individuals to determine if there is a relationship between serum TSH levels and Hospital Anxiety and Depression scale (HAD) scores. We found an interaction between being on thyroxine and the relationship, so the analysis was performed separately in the general population (n=24 363) and in those on thyroxine (n=1387). Analysis was performed using TSH as a continuous variable.
Results: There was a significantly higher prevalence of both depression (18.4 vs 12.8% in females) and anxiety (23.4 vs 18.6%) in subjects on thyroxine. In the general population there was no evidence of a relationship between serum TSH and depression scores in females but a negative association in males (B-coefficient −0.35). There was a significant negative association between serum TSH and anxiety scores in males (B −0.44) and females (B −0.40). People on thyroxine had a very different profile with a positive association between serum TSH and both depression (B +0.25) and anxiety scores (B +0.28).
Conclusions: In addition to a higher prevalence of depression and anxiety in people on thyroxine, the relationship between thyroid function and mood appears to be different in this group.