Neuropsin (NP, kallikrein 8, KLK8)–a kallikrein gene-related (KLK) endoprotease–plays a key role in neuroplasticity processes. Neuropsin expression takes places both extracellularly and inside neurons within the area of the hippocampus. Various forms of electrophysiological stimulation (kindling, LTP, stress) increase neuropsin expression within the hippocampus and in many other regions of the brain (e.g. neocortex, amygdala). Neuropsin is mainly engaged in the early stage of LTP and in the process of synaptogenesis. Social cognition deficits (difficulties with identification, naming and analysing experienced emotional states) in the group of people suffering from depression have been described in scientific papers published in recent years. They are considered the core features of major depressive disorders.

The aim of this study is to link the human neuropsin gene (hNP) expression with the ability of the examined subjects to use nonverbal communication in social interactions.

120 individuals meeting the diagnostic criteria for a recurrent depressive disorders (rDE) were qualified to participate in the study. The Emotional Intelligence Scale–Faces task and two subtests from The Right Hemisphere Language Battery (RHLB) were used in the study.

Significant interrelations between expression on the mRNA level for the hNP gene and the variables used to assess social competences were confirmed. Results of the statistical analysis make it possible to confirm an inversely proportional correlation between the analysed variables.

Increased hNP expression is associated with a reduction of interpersonal abilities in the people affected by depression.

The authors have not supplied their declaration of competing interest.