Mood

Mood is a sustained emotional state that colors perception and behavior over hours to weeks, as distinct from an emotion, which is a brief response to a specific event.

Mood emerges from the interplay of brain circuits involving the prefrontal cortex, amygdala and limbic system, chemical messengers such as serotonin, dopamine and norepinephrine, hormones including cortisol, and the influence of sleep, physical activity, pain, social connection and life events. Normal mood varies from day to day; a mood disorder is diagnosed when low or elevated mood is persistent, out of proportion to circumstances and interferes with functioning, as in major depressive disorder or bipolar disorder.

Clinicians assess mood through interview and standardized questionnaires such as the PHQ-9, and mood is a common secondary outcome in studies of pain, sleep and chronic illness because those conditions and mood affect one another. In pets, mood is inferred from behavior, appetite and engagement. The endocannabinoid system is involved in emotional regulation, and cannabinoids have been studied for effects on mood in early research; THC can produce both elevated and anxious or low mood depending on dose and person.