Hormones are vital for maintaining normal body functions, but scientists are finding they can also powerfully — and sometimes negatively — affect our mood and mental health.
While emotions are often seen as products of conscious control, research shows that hormones, like neurotransmitters, can shape how we think and feel. Some scientists are now exploring how this connection could lead to new treatments for depression, anxiety and other mood disorders.
Hormones are chemical messengers released by glands and organs that travel through the bloodstream to trigger specific biological responses. More than 50 hormones have been identified, managing key processes including growth, reproduction, metabolism, sleep, and mental wellbeing.
“Hormones really impact our mood and emotions,” said Nafissa Ismail, professor of psychology at the University of Ottawa. “They interact with neurotransmitters in specific brain regions and influence processes like neurogenesis – the birth of new neurons.”
Hormonal changes and mental health
Depression, anxiety and post-traumatic stress disorder (PTSD) are more common during major hormonal shifts, especially in women. Though boys and girls have similar depression rates in childhood, adolescent girls are twice as likely to experience it — a pattern that continues throughout life.
Falling oestrogen and progesterone levels before menstruation can trigger irritability, sadness and anxiety in many women. For some, this manifests as premenstrual dysphoric disorder (PMDD), a severe mood disorder marked by extreme emotional swings and depression.
“PMDD can profoundly affect people’s lives every month,” said Liisa Hantsoo, assistant professor of psychiatry at Johns Hopkins University.
Conversely, high oestrogen levels before ovulation are linked to happiness, while a hormone derived from progesterone, allopregnanolone, has calming effects. Fluctuations during pregnancy, perimenopause and menopause can also disrupt mental health — up to 13% of new mothers experience post-partum depression, often linked to a sudden drop in hormones after childbirth.
“It’s not about the exact hormone level, but how sharply those levels rise or fall,” said Liisa Galea, professor of psychiatry at the University of Toronto. “Some people are more sensitive to fluctuations than others.”
Men also experience gradual declines in testosterone with age, which can contribute to mood changes. “This topic doesn’t get enough attention,” said Ismail.
How hormones alter the brain
Sex hormones can boost mood by increasing serotonin and dopamine — chemicals tied to pleasure and motivation. Oestrogen also protects neurons and promotes growth in the hippocampus, the brain’s emotional and memory centre. Loss of neurons in this area has been linked to depression and Alzheimer’s disease.
When women reach menopause, oestrogen withdrawal can lead to “brain fog” and memory lapses.
The stress connection
Hormones also regulate stress through the hypothalamus-pituitary-adrenal (HPA) axis. When stressed, the brain triggers cortisol release to help the body cope. Chronic stress, however, keeps cortisol levels high, damaging brain regions like the hippocampus, amygdala and prefrontal cortex — which weakens memory, decision-making, and emotional control.
“The amygdala helps us control our emotions,” said Ismail. “When it shrinks, irritability and emotional instability increase.”
Oxytocin, often called the “love hormone,” can counter stress by promoting feelings of safety and bonding. Though its exact brain mechanism remains debated, studies suggest oxytocin can make people more trusting and empathetic.
Meanwhile, imbalances in thyroid hormones (T3 and T4) can lead to anxiety or depression. Correcting these levels often restores mood. “Doctors usually check hormonal profiles in patients with mood changes,” Ismail noted.
Towards hormone-based therapies
Understanding how hormones influence mood is paving the way for new treatments. The drug Brexanolone, which mimics allopregnanolone, has proven effective for post-partum depression.
Hormone replacement therapy (HRT) can improve mood for some menopausal women, while testosterone supplements may enhance antidepressant effects in men. However, hormonal birth control can either help or worsen PMDD symptoms, showing that individual sensitivity still varies widely.
“We know hormones affect mood, but we need to learn exactly how,” Ismail said. “Antidepressants targeting serotonin don’t work for everyone — especially adolescents — so understanding hormonal and developmental differences could lead to more effective solutions.”
