Depression linked to lower levels of a hormone that helps resilience

Researchers at McGill University have discovered the first evidence of a connection between noradrenergic neurons — which affect our attention levels and alertness — and vulnerability to depression.

The study, which has been published in the journal Nature Neuroscience, could lead to a new type of depression treatment that targets the adrenergic system.

Resilience — a biological mechanism that determines an individual’s capacity to rebound from stressful or traumatic events — plays a large part in a person’s vulnerability to depression.

Bruno Giros, whose team is part of the research network that made the discovery, said: ‘We know that a small cerebral structure, known as the ventral tegmental area, contains dopaminergic neurons that play a key role in vulnerability to depression. By mimicking stressful life events in animal models, the researchers confirmed that increased dopaminergic neuron activity corresponds to depression.’

Noradrenergic neurons are located in a cerebral structure named locus coeruleus. These neurons communicate with each other using noradrenaline, a chemical involved in emotional regulation, sleep and mood disorders and, according to the researchers, resilience and depression.

By putting the neurons under various stress tests, Giros’s team showed that animals that cannot release noradrenaline are more vulnerable to depression following episodes of stress.

‘Beyond this discovery about the brain mechanisms involved in depression, our results help explain how adrenergic drugs may work and could be used to treat major depression.’ Giros said.