A study of 1.1 million Swedish fathers found that men were actually less likely to receive psychiatric diagnoses during pregnancy and the early months after birth. Then came month 10–12. Depression and stress-related disorders rose more than 30% above pre-pregnancy levels — the delayed hit that surprised the researchers themselves.
The study, published in JAMA Network Open in March 2026 by scientists at Karolinska Institutet and Sichuan University, tracked when Swedish fathers received new psychiatric diagnoses from one year before pregnancy through their child's first birthday. The early months looked stable — even protective. Then the trend reversed.
Lead researcher Jing Zhou described the finding as unexpected: "Many cherish the intimate moments with their child, whilst at the same time the relationship with their partner may be affected and sleep quality may deteriorate, which can contribute to an increased risk of mental ill-health." The toll, it turns out, is cumulative — not immediate.
The practical implication is easy to miss. A new dad who seems fine in the first few months may genuinely be fine. Or he may be running on adrenaline, novelty, and the social pressure to look like he's handling it. By month 10, the sleep debt is real, the excitement has settled into routine, and nobody's checking in anymore.
The researchers also note their data only captures men who sought clinical care — meaning the actual numbers are likely higher. Postnatal depression has long been discussed for new mothers. This study is a reminder that the window for fathers is different, and longer.
Source: Karolinska Institutet / JAMA Network Open, March 24, 2026
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