Many of our moods depend on our nervous system. Too much or too little of the chemicals that speed things up or slow things down and the whole thing can go out of kilter. The basis of many of our medications is to correct these imbalances. Here are just a handful of the essential neurotransmitters and the way they work.
Glutamate and GABA can be thought of as mainstay neurotransmitters. They exist in high concentrations within the brain where one (glutamate) is the throttle and the other gamma amino butyric acid (GABA) acts as the brake. Glutamate has an important role in learning and memory but too much and it can lead to agitation, impulsive behavior and even violence. GABA has the opposite effect – it is the anti-stress, anti-anxiety, anti-panic, anti-pain neurotransmitter. It increases our levels of tranquility by inhibiting too much nerve activity and helps us fall asleep. Some of the most frequently used drugs for anxiety enhance the action of GABA.
Serotonin is all about serenity and hopefulness in moods. Serotonin is probably the most famous neurotransmitter because of the antidepressants that boost it up. Receptors for serotonin show up in the intestines (it makes food move through faster), blood vessels (increases constriction--and blood pressure and migraines), and of course the central nervous system. High serotonin levels lower appetite.
When levels of serotonin are low, our ability to sleep is disturbed and we can't feel pleasure in anything. We crave carbohydrates. Low levels are linked to depression, obsessive compulsive disorder, violence, aggression, and suicide. And low levels of serotonin are linked to panic disorder. Weirdly, low levels of serotonin may also lead to urinary frequency, hyperactive bladder, and urge incontinence. In the past they knew that women with bladder problems were depressed, but they thought the bladder problems caused the depression. Now, however, it looks as though both could be caused by low serotonin levels.
The latest generation of SSRI drugs, such as Prozac, aim to increase levels of serotonin within the brain. Low levels of serotonin are associated with depression.
Dopamine is our arousal and stimulation neurotransmitter. We associate dopamine with rewards as it controls our appetite for sex, eating, pleasure and even creative thinking. Too little dopamine can lead to depression but too much can lead to dependence on the agent doing the stimulating. Cocaine, for example, increases dopamine levels in the brain’s reward circuit and, for a period, can produce intense pleasure. Long-term use seems to result in neural degeneration from overproduction of dopamine.
Endorphins are both hormones and neurotransmitters and they can pack a punch. We have at least 20 different types of endorphins some of which are more powerful than morphine. We tend to release endorphins when we’re under stress or in pain. The higher the level of endorphin the less pain we feel and the more relaxed, even euphoric, we can become. Foods like chocolate or chilli peppers enhance the secretion of endorphins. Perhaps it isn’t surprising that we associate chocolate with comfort and pleasure.
Norepinephrine (Noradrenaline) is the main neurotransmitter of the sympathetic nervous system. We associate this with our fight-or-flight mechanism and moderation of other physical actions such as heart rate and blood pressure. Too little norepinephrine and we become sleepy and lethargic. Too much and our thoughts run away with us, we become twitchy and nervous, our hands and feet go cold and our blood pressure climbs.
Acetylcholine isn't one of the main mood neurotransmitters, but it is high during the fight or flight response, helps with alertness, and is released during REM sleep, so it probably plays a role in mood that they haven't figured out yet.
Other chemicals called hormones may affect the delicate balance of chemicals in the brain. The potential relationship between depression and hormones focuses on 3 main areas: the fight-or-flight response, the thyroid hormones, and the sex hormones.
Frequently activated fight-or-flight response. Your body's hormone system regulates your response to stress. When you're under stress or perceive a threat, your hypothalamus - the area of the brain that regulates the release of hormones from glands throughout your body - increases production of a substance called corticotropin releasing factor, or CRF. CRF causes the pituitary and adrenal glands to increase the secretion of hormones that cause the body to be on alert and ready to defend itself, including the stress hormone cortisol. That means your muscles tense, your breathing becomes shallow, and your senses become sharper. Studies have shown that when this often-called fight-or-flight stress response is activated frequently, it may lead to depression. Experts have found that the hormone system is often overactive in many depressed people and that antidepressant medications can reduce CRF levels.
Over - or understimulation of thyroid hormones. The thyroid gland produces important hormones that can affect depression. An overactive thyroid, a condition called hyperthyroidism, can cause overproduction of hormones and result in symptoms such as anxiety, nervousness, and insomnia. An underactive thyroid, a condition called hypothyroidism, can cause depression and result in fatigue, mental slowness, and other symptoms.
Sex hormones. Sex hormones, especially female hormones, may be associated with depression. Childbirth, the menstrual period, and menopause all cause hormonal changes that may be linked to depression. Depression among women increases during times of hormonal change, such as after childbirth. Research suggests that 4 out of 10 women experience mood changes before their menstrual cycle. Approximately 5% of women experience serious depression during premenstrual periods. Talk with your healthcare provider if you feel depressed around your period, during pregnancy, after childbirth, or around the time of menopause. Also let your healthcare provider know if you feel depressed after starting hormone medications such as birth control pills or hormone replacement therapy.