Psychosexual development is profoundly shaped by a network of hormonal signals that influence brain organization, behavior, and social interactions. Among these, sex steroid hormones, neuropeptides, and glucocorticoids play central roles in shaping motivational circuitry during critical windows of perinatal and pubertal brain development. Insights from modern developmental neuroendocrinology and behavioral genetics serve as a new foundation through which to understand Freud’s five stages of psychosexual development. The oral stage is primarily shaped by the organizational effects of sex hormones on perinatal brain development, and by oxytocin’s role in attachment formation. The anal stage centers on bodily control, mediated by cortical development and influenced by stress exposure. The phallic stage is characterized by the emergence of gender identity and psychological sex differences, where neuropeptides such as oxytocin and vasopressin play critical roles facilitating the development of prosociality and aggression. The latency stage marks the beginning of adrenal puberty, improved executive functioning, and environmental influences on pubertal timing. The genital stage represents a critical period of brain and behavioral reorganization driven by puberty, whereby androgens and estrogens orchestrate the development of secondary sexual characteristics, sex drive, neural reward circuitry, and sex differences in risk-taking and anxiety. Taken together, Freud’s theory of psychosexual development is revised under modern empirical constraints in the spirit of his Project for a Scientific Psychology.
