Mustard, Gentian, Gorse…
References :

Rescue Remedy mother tincture, 2 drops on the tongue twice a day for a month should do the trick.

Safe and no side effects.
References :

http://www.shen-nong.com/eng/pdf/01012007.pdf
References :

Depression is the most prevalent of all the emotional disorders. This may vary from feelings of slight sadness to utter misery and dejection. It brings together a variety of physical and psychological symptoms which together constitute a syndrome.

Depression is the most unpleasant experience a person can endure. It is far more difficult to cope with than a physical ailment. The growing complexities of modern life and the resultant crisis, as well as mental stress and strain in day-to-day living, usually leads to this disorder. It also arises out of the monotony and drudgery of a daily routine, without any meaningful variation in urban life. Suicide is the major risk in extreme cases of depression.

Symptoms: It is not always easy to diagnose depression clinically. The most striking symptoms of depression are feelings of acute sense of loss and inexplicable sadness, loss of energy, and loss of interest. The patient usually feels tired and lacks interest in the world around him. Sleep disturbance is frequent. Usually the patient wakes up depressed at 4 or 5 in the morning and is unable to return to sleep. Other disturbed sleep patterns are difficulty in getting off to sleep on going to bed at night, nightmares and repeated waking from midnight onwards.

The patient often suffers from guilt, oppressive feelings, and self-absorption. Other symptoms of depression are: loss of appetite, giddiness, itching, nausea, agitation, irritability, impotence or frigidity, constipation, aches and pains all over the body, lack of concentration and lack of power of decision. Some persons may lose interest in eating and suffer from rapid loss of weight while others may resort to frequent eating and as a result gain in weight.

Cases of severe depression may be characterized by low body temperature, low blood pressure, hot flushes, and shivering.

The external manifestations represent a cry for help from the tormented mind of the depressed persons. The severely depressed patient feels worthless and is finally convinced that he himself is responsible for his undoing and his present state of hopeless despair.

Causes: Depleted functioning of the adrenal glands is one of the main causes of mental depression. Irregular diet habits cause digestive problems and lead to the assimilation of fats. An excess of carbohydrates like cereals, white sugar, coffee, tea, chocolates and comparatively less quantities of vegetables and fruits in the diet may result in indigestion. Due to indigestion, gases are produced in the digestive tract, causing compression over the diaphragm in the region of the heart and lungs. This in turn, reduces the supply of oxygen to the tissues, which raises the carbon dioxide level, causing general depression.

The excessive and indiscriminate use of drugs also leads to faulty assimilation of vitamins and minerals by the body and ultimately causes depression. The use of aspirin leads to deficiencies of vitamin C and antacids can cause deficiencies of calcium and vitamin B. Diabetes, low blood sugar (hypoglycemia) and weakness of the liver resulting from the use of refined or processed foods, fried foods, and an excessive intake of fats may also lead to depression.

The Cure: The modern medical system treats depression with anti-depression drugs which provide temporary relief but have harmful side-effects and do not remove the causes or prevent its recurrence. The harmful side effects include gross liver damage, hypersensitivity, insomnia, hallucinations, a confused state, convulsions, a fall in blood pressure which brings on headaches and dizziness , blurred vision, difficulty in inhaling and urine retention. The plan of action for self-treatment of depression consists of regulating the diet, exercise, scientific relaxation, and meditation.

Diet has a profound effect on the mental health of a person. Even a single nutritional deficiency can cause depression in susceptible people. Dr. Pricilla, associate clinical professor at the University of California, prescribes nutritional therapy to build up brain chemicals, such as serotonin and norepinephrine that affect mood and are often lacking in depressed people. She recommends eating foods rich in B vitamins, such as whole grains, green vegetables, eggs and fish.

The diet of persons suffering from depression should completely exclude tea, coffee, alcohol, chocolate, and cola, all white flour products, sugar, food colorings, chemical additives, white rice, and strong condiments. The diet should be restricted to three meals. Fruits can be taken in the morning for breakfast with milk and a handful of nuts and seeds. Lunch may consist of steamed vegetables, whole-wheat chappatis and a glass of buttermilk. For dinner, green vegetable salad and all available sprouts such as alfalfa seeds, mung, cottage cheese or a glass of buttermilk would be ideal.

Activity and Exercise: The depressive mood can be overcome by activity. Those who are depressive will forget their misery by doing something. They should turn away from themselves and consider others. At home they can take to decorating, repairing or constructing something new. The pleasure of achievement overcomes the distress of misery.

Exercise also plays an important role in the treatment of depression. It not only keep the body physically and mentally fit but also provides recreation and mental relaxation, it is nature’ best tranquilizer. According to Dr. Robert Brown, a clinical associate professor at the University of Virginia School of Medicine. "Exercise produces chemical and psychological changes that improves your mental health. It changes the levels of hormones in blood and may elevate your beta-endorphins(mood-affecting brain chemicals). Exercise may also improve the function of the autonomic nervous system."

Exercise also gives a feeling of accomplishment and thus reduces the sense of helplessness. Some form of active exercise, must be undertaken each day at a regular hour. To be really useful, exercise should be taken in such a manner as to bring into action all the muscles of the body in a natural way. Walking is one such exercise. It is, however, so gentle in character that one must walk several kilometers in a brisk manner to constitute a fair amount of exercise. Yogic asanas such as vakrasana, bhujangasana, shalabhasana, halasana, paschimottanasana, sarvangasana and shavasana and pranayamas like kapalbhati, anuloma-viloma and bhastrika are highly beneficial in the treatment of depression.

Relaxation and Meditation: The patient must gain control over his nervous system and chanelize his mental and emotional activities into restful harmonious vibrations. This can be achieved by ensuring sufficient rest and sleep under right conditions. He must also learn the art of scientific relaxation and meditation which will go a long way in curing depression.

Relaxation enables the muscles to work more efficiently and eliminates fatigue by promoting venous blood circulation throughout the body. The best method of relaxation is to practice shavasana or the ‘dead pose.’ The procedure for this asana has been outlined in chapter 7 on yoga therapy.

Meditation involves training the mind to remain fixed on a certain external or internal location. All the mental faculties should be directed, without cessation, towards the object of meditation. It can be achieved by constant practice. It will be advisable to meditate on God or Atman as one becomes imbued with the quality of the object on which one meditates.

Meditation will help create an amount of balance in the nervous system. This would enable the glands to return to a correct state of hormonal balance and thereby overcome the feeling of depression. Regularity of time, place and practice are very important in meditation. Regularity conditions the mind to slowing down its activities with a minimum delay. The most effective times are early dawn and dusk, when the atmosphere is serene and peaceful.

A neutral immersion bath for one hour daily is also helpful in the treatment of depression. This bath is administered in a bathtub which should be properly fitted with hot and cold water connections. The patient should lie in the tub after filling it with water at a temperature ranging from 92 o to 98 o F. The head should be kept cold with a cold compress.

Good Luck
References :
Research Study.