Neurons called noradrenergic control the response toward resilience or toward vulnerability to depression, according to a study published in the journal Nature Neuroscience. The study was led by Bruno Giros, a researcher at the Douglas Mental Health University Institute and a professor of psychiatry at McGill University. He is also the first one to show the connection between these neurons and depression, laying the foundation toward new strategies that target the adrenergic system to treat depression.

Risk factors for depression vary for each person and not everyone may necessarily suffer major depression from losing a job, accidents, death of a loved one, bullying and other stressful events. Experts say that the ventral tegmental area of the brain, a small cerebral structure, is the key to resilience, which dictates a person’s ability to recover from distressing circumstances. This structure contains dopaminergic neurons that regulate vulnerability to depression, according to Giros.

The research team, who are part of the Centre intégré universitaire de santé et de services sociaux (CIUSSS) de l’Ouest-de-l’Île-de-Montréal research network, also found out that a second type of neuron controls the dopaminergic neuron activity. After simulating traumatic events in their animal models, they concluded that increased dopaminergic neuron activity makes one more prone to depression.

These neurons are found in the Locus coeruleus, a small nucleus located in the pons (part of the brainstem). The noradrenergic neurons relay information with each other by using a neurotransmitter called noradrenalin, which is involved in regulating emotions, sleep and mood disorders and now, resilience and depression.

The research team confirmed that chronic stress makes animals that cannot release noradrenalin more prone to suffering from depression through employing pharmacological and genetic techniques as well as using light beam to activate neuron activity, called the optogenetic approach.

Giros adds that the findings can help scientists understand how adrenergic drugs function. Eventually, this information will help in the development of new treatments to cure major depression.