Dogs can sense depression. Chronic stress and depression are linked to low serotonin, norepinephrine, and dopamine levels in the brain. These are the neurotransmitters responsible for mood and feelings related to pleasure.
Research shows that patients with major depression often have increased levels of monoamine oxidase A. This enzyme breaks down serotonin, dopamine, and norepinephrine, resulting in deficient levels of these neurotransmitters.
Dogs can smell a surge of hormones (adrenaline and cortisol) caused by stress or a drop in hormones when we feel depressed, sensing our emotions. When they sense depression, many dogs respond by acting differently toward their owners – they sit beside them or put a head on a person’s lap to show support.