Unintended consequences of inhibiting dihydrofolate reductase through folic acid supplementation: inattentive-type attention deficit hyperactivity disorder and ASD connections

Does L-Methylfolate Supplement Methylphenidate Pharmacotherapy in Attention-Deficit/Hyperactivity Disorder?: Evidence of Lack of Benefit From a Double-Blind, Placebo-Controlled, Randomized Clinical Trial

PURPOSE/BACKGROUND

Interventions for attention-deficit/hyperactivity disorder (ADHD) may be inadequate for some patients. There is evidence that supplementation with L-methylfolate augments antidepressant agent effects and thus might also augment ADHD treatment effects by a common catecholaminergic mechanism.

METHODS

Forty-four adults with Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of ADHD participated in a randomized, double-blind, placebo-controlled, 12-week trial of 15 mg of L-methylfolate in combination with osmotic-release oral system methylphenidate. Osmotic-release oral system methylphenidate was dose optimized over the first 6 weeks. We evaluated the effects on ADHD symptoms, self-report on the Behavior Rating Inventory of Executive Function of executive function, methylphenidate dosing, neuropsychological test measures, the Adult ADHD Self-report scale, emotional dysregulation, social adjustment, and work productivity, as well as moderating effects of body mass index, autoantibodies to folate receptors, and select genetic polymorphisms.

RESULTS

L-Methylfolate was well tolerated, with no significant effect over placebo except improvement from abnormal measures on the mean adaptive dimension of the ASR scale (χ = 4.36, P = 0.04). Methylphenidate dosing was significantly higher in individuals on L-methylfolate over time (χ = 7.35, P = 0.007). Exploratory analyses suggested that variation in a guanosine triphosphate cyclohydrolase gene predicted association with higher doses of methylphenidate (P < 0.001).

CONCLUSIONS

L-Methylfolate was associated with no change in efficacy on measures relevant to neuropsychiatric function in adults with ADHD, other than suggestion of reduced efficacy of methylphenidate. Further investigation would be required to confirm this effect and its mechanism and the genotype prediction of effects on dosing.