Dopaminergic function and the cortisol response to dexamethasone in psychotic depression

1. It has been hypothesized that psychotic symptoms in depression may be due to increased dopamine activity secondary to hypothalamic-pituitary-adrenal (HPA) axis overactivity. 2. To test this hypothesis, the authors examined the cortisol response to dexamethasone suppression test (DST, 1 mg orally) and multihormonal responses to apomorphine (APO, 0.75 mg s.c.)--a dopamine agonist--in 150 drug-free hospitalized patients with DSM-IV major depressive episode with psychotic features (MDEP, n=35), major depressive episode without psychotic features (MDE, n=74), or schizophrenia paranoid type (SCZ, n=41), and 27 hospitalized healthy controls (HCs). 3. MDEPs showed increased activity of the HPA system (i.e. higher post-DST cortisol levels) than HCs, SCZs and MDEs. However, there were no differences in adrenocorticotropic hormone (ACTH), cortisol, prolactin and growth hormone (GH) responses to APO between MDEPs and MDEs and HCs. On the other hand, SCZs showed lower APO-induced ACTH stimulation and a higher rate of blunted GH than HCs, MDEs and MDEPs, suggesting a functional alteration of the hypothalamic dopamine receptors in SCZs. 4. In the total sample and in each diagnostic group, DST suppressors and non-suppressors showed no differences in hormonal responses to APO. 5. These results suggest a lack of causal link between HPA axis hyperactivity and dopamine dysregulation. In contrast to schizophrenia, psychotic symptoms in depression seem not to be related to dopamine function dysregulation.