Understanding Depression

Depression is one of the most common health conditions in Aotearoa New Zealand — and one of the most misunderstood. It's not just feeling sad or having a bad week. Clinical depression is a persistent state that affects mood, energy, sleep, appetite, concentration, and a person's basic sense of motivation, often lasting for weeks or months at a time. It's also, importantly, treatable — and understanding why it happens can make it much easier to know where to turn for help.

How common is depression in New Zealand?

More common than most people realise, and rates have been climbing. In the 2021–23 New Zealand Health Survey, about 1 in 3 adults (34.8%) reported mild or greater anxiety and/or depression symptoms in the previous two weeks — up from around 1 in 4 (25.0%) just five years earlier. Separately, 14.3% of adults reported high or very high psychological distress in 2024/25, roughly double the rate seen in 2019/20, and women were more likely to be affected than men.

Some groups carry a heavier load. Distress rates are notably higher among young adults aged 15–24 (22.9%), Māori (22.5%), Pacific peoples (23.8%), and disabled adults (35.5%). And access remains a real problem: roughly 1 in 10 adults wanted professional help for their mental health in the past year but didn't get it. Globally, the picture is similar — the World Health Organization estimates around 332 million people worldwide live with depression, about 4% of the population, with women affected roughly 1.5 times more often than men. The gap between how common depression is and how many people get support is exactly where accessible, timely therapy and counselling make a difference.

What actually causes depression?

There's no single cause. The leading scientific understanding today is the biopsychosocial model — depression usually comes from a mix of factors working together, not one thing alone:

  • Biological factors — genetics (research suggests genes account for roughly a third of the risk), changes in brain circuits that regulate mood and reward, disrupted stress-hormone regulation, low-grade inflammation, and reduced brain adaptability.

  • Psychological factors — patterns of negative thinking, difficulty processing emotions, and coping styles often learned early in life, sometimes shaped by difficult relationships or experiences.

  • Social and environmental factors — ongoing stress, loss, trauma, isolation, financial hardship, and major life disruptions. In the New Zealand context, this also includes things like housing pressure, the cost of living, rural isolation, and — for Māori and Pacific communities in particular — the effects of colonisation, discrimination, and disconnection from culture and whānau.

Many mental health services here also work within holistic frameworks such as Te Whare Tapa Whā (the "four-sided house" model developed by Sir Mason Durie), which understands wellbeing as resting on four connected pillars: physical health (taha tinana), mental and emotional health (taha hinengaro), family and social connection (taha whānau), and spiritual wellbeing (taha wairua). That framing is a useful reminder that treating depression well often means looking beyond symptoms alone.

Wait — didn't they debunk the ;chemical imbalance; theory?

Sort of, and it's worth understanding what actually happened, because a lot of what circulates online oversimplifies it.

For decades, the most common public explanation for depression was that it's caused by a ‘chemical imbalance’ — specifically, too little serotonin in the brain. This idea took hold in the late 1960s and became a convenient shorthand used in doctor's offices, drug ads and everyday conversation, even though most researchers had already moved past it as an oversimplification well before it made headlines again.

In 2022, a major review of the evidence — led by psychiatrist Joanna Moncrieff — pulled together decades of studies and concluded there was no consistent evidence that low serotonin causes depression. It made international news, and a lot of people took it to mean the chemical imbalance idea had been fully debunked.

The more accurate picture is a bit more nuanced. Other scientists have since published detailed critiques of that 2022 review, questioning some of its methods and conclusions — so it's not settled science on either side. What virtually everyone in the field agrees on, though, is this: no single brain chemical explains depression. Today's understanding treats serotonin as just one part of a much bigger picture that also includes other neurotransmitters, stress hormones, inflammation, and brain adaptability — all interacting differently from person to person.

Importantly, this doesn't mean antidepressant medication doesn't work. Clinical trials still show it genuinely helps many people, especially with moderate to severe depression, and in New Zealand it's usually prescribed and monitored through a GP or psychiatrist. It just means the old ‘your brain is missing a chemical’ explanation was always too simple — and medication tends to work best as one part of a broader treatment plan, alongside therapy, rather than a standalone fix.

Three ways of understanding depression — and why they work together

Psychologically, depression often involves a cycle: negative thinking leads to withdrawal and inactivity, which reinforces the negative thinking. Difficult past relationships and unmet emotional needs can also make someone more vulnerable. This is the foundation for therapies like cognitive-behavioural therapy (CBT) and interpersonal therapy, both of which have decades of research showing they work — often as well as medication, with longer-lasting effects.

Medically, as covered above, depression involves real, measurable changes in the brain and body — but as one part of a bigger, more individual picture rather than a single fixable defect.

Psychoanalytically, the focus shifts from symptoms to meaning. Going back to Freud's early writing on grief and loss, this tradition looks at how unconscious conflict, unresolved loss, or a fragile sense of self-worth — often shaped by early relationships — can express itself as depression. Rather than aiming for quick symptom relief, this approach works toward deeper self-understanding. Longer-term psychodynamic therapy has been shown to offer meaningful, lasting benefit, particularly for more complex or recurring depression.

The bottom line

No single explanation — psychological, medical, or psychoanalytic — tells the whole story on its own. Depression is common in New Zealand, it's backed by real and evolving science, and above all, it responds to treatment. The right approach is different for everyone, which is exactly why working with a therapist or counsellor to figure out what fits you is often the most effective first step. A good starting point is usually your GP, who can assess what you're going through and refer you to funded or appropriate services.

If you're noticing persistent low mood, loss of interest in things you used to enjoy, changes in sleep or appetite, or a sense of hopelessness that isn't lifting, reaching out for support is a meaningful and worthwhile step to take.

References

Jauhar, S., Arnone, D., Baldwin, D. S., Bloomfield, M., Browning, M., Cleare, A. J., Corlett, P., Deakin, J. F. W., Erritzoe, D., Fu, C., Fusar-Poli, P., Goodwin, G. M., Hayes, J., Howard, R., Howes, O. D., Juruena, M. F., Lam, R. W., Lawrie, S. M., McAllister-Williams, H., . . . Cowen, P. J. (2023). A leaky umbrella has little value: Evidence clearly indicates the serotonin system is implicated in depression. Molecular Psychiatry, 28(8), 3149–3152. https://doi.org/10.1038/s41380-023-02095-y

Ministry of Health NZ. (2024). New insights into New Zealanders' mental health and problematic substance use. https://www.health.govt.nz/news/new-insights-into-new-zealanders-mental-health-and-problematic-substance-use

Ministry of Health NZ. (2025). Annual update of key results 2024/25: New Zealand Health Survey. https://www.health.govt.nz/publications/annual-update-of-key-results-202425-new-zealand-health-survey

Möller, H.-J., & Falkai, P. (2023). Is the serotonin hypothesis/theory of depression still relevant? Methodological reflections motivated by a recently published umbrella review. European Archives of Psychiatry and Clinical Neuroscience, 273(1), 1–3. https://doi.org/10.1007/s00406-022-01549-8

Moncrieff, J., Cooper, R. E., Stockmann, T., Amendola, S., Hengartner, M. P., & Horowitz, M. A. (2023). The serotonin theory of depression: A systematic umbrella review of the evidence. Molecular Psychiatry, 28(8), 3243–3256. https://doi.org/10.1038/s41380-022-01661-0

Te Hiringa Mahara — Mental Health and Wellbeing Commission. (2025). NZ Health Survey 2024/2025 mental health and substance use data summary. https://www.mhwc.govt.nz/our-work/wellbeing/nz-health-survey-mental-health-and-substance-use-data/

World Health Organization. (2025). Depressive disorder (depression). https://www.who.int/news-room/fact-sheets/detail/depression

Need support right now, in New Zealand?

This content is for general informational purposes and isn't a substitute for professional diagnosis or care.

  • 1737 — free call or text, any time, 24/7, to talk with a trained counsellor

  • Depression Helpline — 0800 111 757 or free text 4202

  • Lifeline — 0800 543 354 or free text 4357 (HELP)

  • Suicide Crisis Helpline (0508 TAUTOKO) — 0508 828 865

  • Youthline — 0800 376 633 or free text 234

  • If you or someone else is in immediate danger, call 111

If you're currently in crisis or having thoughts of harming yourself, please reach out to one of these services or emergency services right away.