It rather depends on the cause.... once this is identified the the course of action is obvious. Have a look to the past and the successful work of Abraham Hoffer. No amount of psychological intervention can help a person with a poisoned or starving brain. Assist healing and a person will self heal. Here is a list of causes I have identified:

Known indirect risks:

Childhood trauma, grief and loss, accident, abuse; both physical and sexual, hormonal turmoil of adolescence, relationship distress, overwhelm, depression, loss of meaning, substance abuse, addictions, gambling, dramatic change, seasonal, childbirth, financial worries, over work or shift work, jet lag, loss of child/job/home/parents/family/friend, illness, cancer, chronic pain, tooth infection, natural disaster, war, hormone imbalance, menopause, loneliness, self-neglect and dementia. Dramatic life changes, infatuation, sudden large financial gain, spiritual crisis, sudden fame, near death experiences and even too much sunshine.

Known direct causes:

Rabies, Toxoplasmosis (very common and caught from cat excrement), Lymes disease, Pyroluria, Porphyria, parasites, heavy metal exposure (mercury, lead and others). Head injury, fetal alcohol syndrome, autism's, epilepsy and vaccine damage, high fever, dehydration, sleep deprivation, nutritional deficiency, mineral deficiency, ab-reaction to recreational and prescription drugs and stimulants. Side/direct effects from mental health drugs, other medical drugs. Incorrect use of nicotine patches, post-operative psychosis and post traumatic shock. Blood sugar imbalance, over or under active thyroid, faulty methylation and B vitamin deficiency, essential fats deficiencies, histamine excess, serotonin deficiency, adrenal imbalance, acetylcholine imbalance, toxic poisoning overload and gut inflammation, bladder infection, metallothionein deficiency, direct food allergies, extreme physical and emotion exhaustion and extreme hypothermia.