Association of Prolactin, Oxytocin, and Homocysteine With the Clinical and Cognitive Features of a First Episode of Psychosis Over a 1-Year Follow-Up

Abstract

Background: The clinical debut of schizophrenia is frequently a first episode of psychosis (FEP). As such, there is considerable interest in identifying associations between biological markers and clinical or cognitive characteristics that help predict the progression and outcome of FEP patients. Previous studies showed that high prolactin, low oxytocin, and high homocysteine are factors associated with FEP 6 months after diagnosis, at which point plasma levels were correlated with some clinical and cognitive characteristics.

Methods: We reexamined 75 patients at 12 months after diagnosis to measure the evolution of these molecules and assess their association with clinical features.

Results: At follow-up, FEP patients had lower prolactin levels than at baseline, and patients treated with risperidone or paliperidone had higher prolactin levels than patients who received other antipsychotic agents. By contrast, no changes in oxytocin and homocysteine plasma levels were observed between the baseline and follow-up. In terms of clinical features, we found that plasma prolactin and homocysteine levels were correlated with the severity of the psychotic symptoms in male FEP patients, suggesting that they might be factors associated with psychotic symptomatology but only in men. Together with oxytocin, these molecules may also be related to sustained attention, verbal ability, and working memory cognitive domains in FEP patients.

Conclusion: This study suggests that focusing on prolactin, oxytocin, and homocysteine at a FEP may help select adequate pharmacological treatments and develop new tools to improve the outcome of these patients, where sex should also be borne in mind.

Keywords: First-episode psychosis; cognition; homocysteine; oxytocin; prolactin.

Figure 1.

Mean differences ± SEM of the biological markers in the plasma from first-episode psychosis (FEP) patients at baseline and at follow-up. (A, D, G) Plasma prolactin (baseline n = 90; follow-up n = 58), oxytocin (baseline n = 80; follow-up n = 64) and homocysteine (baseline n = 80; follow-up n = 63) in the total group, including women and men. (B, C) Plasma prolactin in women (baseline n = 26; follow-up n = 17) and men (baseline n = 64; follow-up n = 41). (E, F) Plasma oxytocin in women (baseline n = 24; follow-up n = 19) and men (baseline n = 56; follow-up n = 45). (H, I) Plasma homocysteine in women (baseline n = 23; follow-up n = 17) and men (baseline n = 57; follow-up n = 46). A Mann-Whitney U-test or a t test were used to compare the groups: *P <.05; **P <.01. B, baseline; F, follow-up.

Figure 2.

Mean differences ± SEM of plasma prolactin from first-episode psychosis (FEP) patients at baseline and at follow-up (dotted bars). Plasma prolactin from antipsychotic naïve patients (white bar, baseline n = 18; follow-up n = 15), patients treated with risperidone or paliperidone (dark grey bar, baseline n = 41; follow-up n = 18), or patients treated with other antipsychotics (grey bar, baseline n = 31; follow-up n = 24). ANOVA was used to compare between the 3 groups (baseline P < .001; follow-up P < .002), and significant post hoc differences were found between all pairs of groups at baseline or at follow-up, between none and risperidone/paliperidone, and between risperidone/paliperidone and others: *P < .05. Also, t tests were used to compare between the baseline and follow-up groups: ^##P < .01.