Depression is more common than many of us might think, and can affect people's ability to do everyday things, feel pleasure or take interest in activities. Gina Webley, one of our members who is based in Kent, outlines how herbs can play a key role in a multi-targeted approach to the treatment of depression.
Depression is a common mental health condition and one of the leading causes of disability. The search is ongoing to understand how depression develops and to find the most effective forms of treatment. It is clear that depression is a complex condition that results from the interaction of biological, environmental, and psychological factors.
The two most common forms of treatment are antidepressant drugs and talking therapies. Both are effective for some people but not others depending on the cause and severity of the depression. The problems that many experience taking antidepressant drugs has led to the search for other forms of treatment. One of these is herbal medicine. The benefits of herbal medicine can be understood by first considering the problems with antidepressant drugs.
There is much debate on the effectiveness of antidepressant drugs. The placebo effect is large, so the actual action of the drug appears relatively small. In randomized controlled trials testing the effectiveness of antidepressant drugs broadly 40% of people feel better when given a placebo as compared to 60% of those given the drug.
Many people suffer side effects from taking antidepressant drugs. Selective serotonin reuptake inhibitors (SSRI’s) have fewer than the older antidepressant drugs, monoamine oxidase inhibitors and tricyclic antidepressants, but still commonly causes nausea, headaches, sleep disturbance, feeling emotionally numb, weight gain and sexual dysfunction. While some of these side effects may resolve others persist and may worsen with long term use. An increase in risk of suicide has been identified in young people given drug treatment for depression.
Long term use of antidepressants can lead to dependence. It is now acknowledged by the Royal College of Psychiatrists that stopping antidepressant drugs can cause unpleasant withdrawal symptoms such as anxiety, confusion and exhaustion that often force patients back to the drugs they hoped they no longer needed. The College’s previous advice of withdrawal over two to four weeks has been extended to a period of months during which drug doses are reduced more slowly.
It is evident that the drawbacks of taking antidepressant drugs are limited effectiveness with some people seeing no benefit, a range of potential side effects, long term use which does not prevent a relapse and increased dependence leading to withdrawal symptoms. Since antidepressant drugs are least effective in those with mild to moderate depression compared to those with more severe forms of depression taking antidepressant drugs may not be the treatment of choice for many with milder forms of depression.Herbal medicines
Herbal medicine has been used to support depression for hundreds of years. More recent evidence demonstrates the effective antidepressant action of individual herbs such as St John’s Wort, Saffron, and Rhodiola 1,2. These herbs are effective, well tolerated, with few side effects, and do not cause dependence and withdrawal symptoms. Each herb contains several active ingredients which work in synergy to provide therapeutic antidepressant action over and above the action of any individual component.
Since depression is a complex condition resulting from a range of contributing factors, regulating a single target may not reduce depression as effectively as targeting multiple systems. The advantage of herbal medicine is that different herbs can be selected with different sites of action and combined in a single formula. This provides a more holistic approach. The herbs selected can be varied depending on the causes of depression to provide an individualised treatment.
Causes of depression and herbal medicine action
There is much debate around the ‘Monoamine Theory of Depression’ which states that depression results from a depletion in the levels of the monoamine neurotransmitters serotonin, norepinephrine, and/or dopamine in the central nervous system. Antidepressant drugs are believed to act by elevating the levels of these neurotransmitters in the brain. However, investigation has not found convincing evidence of a primary dysfunction of a specific monoamine system in patients with depression 3,4.
This has led to the view that depression is not a disease process resulting from abnormality in neurotransmitters such as serotonin 5. SSRI drugs may be no more effective at reducing depression than other drugs that act on the brain such as the anti-anxiety drug Valium. Instead a drug-centred view is proposed in which psychoactive substances that cross the blood brain barrier modify normal mental states and behaviour. These changes in mental state may relieve depression in some people but do not reverse any underlying biochemical imbalance. A broader view is needed of the causes of depression and the ways it can be treated.
Recent preclinical and clinical evidence 1,2,6,7,8 shows that herbal medicine can treat depression by reducing anxiety resulting from chronic stress, decreasing inflammation, restoring sleep and disrupted circadian rhythms, promoting healthy gut bacteria and balancing thyroid and ovarian hormones.
Stress induced anxiety is a common cause of depression and the two often occur together. Treatment to reduce anxiety is therefore an important component in a multi-action approach to treatment. Over activation of the hypothalamic–pituitary–adrenal (HPA) axis in response to chronic stress contributes to symptoms of depression mainly through increased cortisol levels in the blood and enhanced transmission of corticotropin-releasing factor (CRF) in the brain. Rhodiola and Ginseng are adaptogens which can modulate and balance the adrenal response to stress. They show antidepressant action by regulating the activity of the HPA axis and reducing cortisol release. Herbal medicines also reduce anxiety by increasing the levels of the neurotransmitter gamma-aminobutyric acid (GABA). Saffron, Lavender, Chamomile, Lemon balm, Ashwagandha and Valerian are all herbs which can reduce anxiety and depression via a GABAergic mechanism.
The claim that depression is an inflammatory disorder is gaining popularity. This is supported by the fact that many pro-inflammatory marker levels are elevated in depressed patients 9. A persuasive explanation 10 is that inflammation in the body can activate the inflammatory microglial cells in the brain which in turn cause collateral damage to nerve cells in the areas of the brain such as the amygdala which control emotions. Herbs which may reduce depression via an anti-inflammatory action include St John’s Wort, Turmeric, and Ginseng.
Insomnia and disrupted circadian rhythms make individuals susceptible to depression. Herbs which can restore sleep include Valerian, Hops, Wild lettuce, Passionflower, California poppy and Skullcap. Chaste tree acts via increasing the pineal hormone melatonin to improve sleep by circadian rhythm modulation.
The importance of digestion and in particular the composition of the gut microbiome influences brain function and increases the incidence of depression 11. People with depression have lower levels of certain gut bacteria species, particularly those that can produce serotonin and dopamine. Herbs such Barberry improve the composition of gut bacteria and support healthy gut function.
Depression is a complex condition resulting from a range of contributing factors that can disrupt physiological and mental function. Combining herbs which have a range of different actions increases the potential effectiveness of treatment. For example, a herbal formula for the treatment of depression might contain herbs to reduce anxiety, balance cortisol levels, reduce inflammation and promote healthy bacteria in the gut. The combining of different herbs in a formulation targeted to each individual provides an effective and sustainable form of treatment with few side effects.