Copper excess in psychiatric disorders: a focus on mood spectrum disorders and sex

Background: Meta-analyses show increased copper (Cu) levels in major depression disorder. However, the association of Cu biomarkers with clinical classification in other mental health disorders has not been fully explored. Methods: To this aim, we compared an extensive panel of Cu biomarkers, composed of Cu, ceruloplasmin (Cp) Cp activity, Cp specific activity, Cu not bound to ceruloplasmin (non-Cp Cu, also known as 'free' copper) in 171 consecutive patients affected by psychiatric disorders and in 61 healthy controls (HC) using MANOVA adjusting for the effect of sex and age, and studied their association with the clinical scale outcomes at psychiatric examination, namely Global Assessment of Functioning, Clinical Global Impression, and Brief Psychiatric Rating Scale. Results: individuals with psychiatric disorders were classified as 109 patients affected by mood spectrum disorders (MSD), 20 patients with schizophrenia spectrum disorders (SSD), and 42 with personality disorders (PD). Cu and non-Cp Cu were increased in psychiatric individuals than in HC, which also differed among the patients stratified per the clinical classification, being higher in the MSD individuals. The analysis stratified for sex revealed that women from the patient group, and specifically from the MSD group, had increased levels of Cu and non-Cp Cu than healthy women, while no difference was revealed in men. A logistic regression model considering the effect of sex and age revealed that non-Cp Cu could explain 26 % increased odds of having MSD per mu mol/L unit increase (OR = 1.26; p = 0.0008; 95 % CI 1.099-1.436), that reached 40 % when considering only women. This result was driven by non-Cp Cu that correctly classified 64.1 % MSD (70 % in women) individuals vs. HC in a decision tree model, with values higher than 2.1 mu mol/L which could distinguish the majority of MSD patients (86.3 % MSD vs. 13.7 % HC in women). None of the biological variables under study correlated with outcomes of the clinical scales, substances, or alcohol abuse. Conclusion: Current results suggest mild Cu toxicity in women with MSD, as revealed by a value of non-Cp Cu higher than 2.1 mu mol/L, which can be further investigated to assess its potential diagnostic accuracy in bigger and longitudinal cohorts.