Pan LA, Martin P, Zimmer T, Segreti AM, Kassiff S, McKain BW, Baca CA, Rengasamy M, Hyland K, Walano N, Steinfeld R, Hughes M, Dobrowolski SK, Pasquino M, Diler R, Perel J, Finegold DN, Peters DG, Naviaux RK, Brent DA, Vockley J. (2017) AM J Psychiatry 1;174(1) 42-50 doi: 10.1176/appi.ajp.2016.15111500.
Treatment-refractory depression is a devastating condition with significant morbidity, mortality, and societal cost. At least 15% of cases of major depressive disorder remain refractory to treatment. The authors previously identified a young adult with treatment-refractory depression and multiple suicide attempts with an associated severe deficiency of CSF tetrahydrobiopterin, a critical cofactor for monoamine neurotransmitter synthesis. Treatment with sapropterin, a tetrahydrobiopterin analogue, led to dramatic and long-lasting remission of depression. This sentinel case led the authors to hypothesize that the incidence of metabolic abnormalities contributing to treatment-refractory depression is underrecognized.
The authors conducted a case-control, targeted, metabolomic evaluation of 33 adolescent and young adult patients with well-characterized histories of treatment-refractory depression (at least three maximum-dose, adequate-duration medication treatments), and 16 healthy comparison subjects. Plasma, urine, and CSF metabolic profiling were performed by coupled gas chromatography/mass spectrometry and high-performance liquid chromatography electrospray ionization tandem mass spectrometry.
CSF metabolite abnormalities were identified in 21 of the 33 participants with treatment-refractory depression. Cerebral folate deficiency (N=12) was most common, with normal serum folate levels and low CSF 5-methyltetrahydrofolate (5-MTHF) levels. All patients with cerebral folate deficiency, including one with low CSF levels of 5-MTHF and tetrahydrobiopterin intermediates, showed improvement in depression symptom inventories after treatment with folinic acid; the patient with low tetrahydrobiopterin also received sapropterin. None of the healthy comparison subjects had a metabolite abnormality.
Examination of metabolic disorders in treatment-refractory depression identified an unexpectedly large proportion of patients with potentially treatable abnormalities. The etiology of these abnormalities remains to be determined.