Biological causes of anxiety and depression

In addition to numerous psychodynamic, behavioral and cognitive approaches to onset of depression and anxiety, it is thought that biological factors play part in the development of the disorders. The main theories surround the effects of neurotransmitters such as serotonin, and noradrenaline in the body. Neurotransmitters are chemical substances that are released at the junction between neurons, and that affect the transmission of messages in the nervous system – we have many different types of these in our body which are used in both our conscious, and unconscious actions. For example; you may be familiar with the idea of touching a hot pan and immediately drawing your hand away without thinking, this is due to the stimulus (the hot pan) being sent down as a message through your neurons, to the brain, where it reacts with the response of drawing your hand away, now this is just an example of an immediate response, but the neurotransmitters in your body are in constant use, and imbalances in the chemicals that are passed across them are thought to be an important factor consistently in depression and in areas of anxiety.

There are many different forms of anxiety, these may include phobias, OCD, and paranoia, the latter occurs commonly in social situations where people may feel pressured, eg when making a speech or performing. Again although there is no definitive cause of anxiety, -mainly due to the on going nature vs nurture debate- there has been relatively recent research investigating neuroanatomical explanations of the condition. Theories suggest that there may be an increased or decreased number of neurons surrounding the brain area, that the brain structure may be slightly different to individuals without phobias, of that surrounding areas may be slightly more or less active. An area in the brain called the amygdala controls emotion, stress and fear responses, so in phobias particularly anatomy of the amygdala is thought to play a role in the onset.

In more specific anxiety such as OCD there is also some evidence to suggest that areas of the brain called frontal lobes and ganglia appear to be more active in individuals who suffer from OCD. However we have to be careful about how we evaluate evidence, especially in psychology, as it may not compare the same in all individuals, hence why it is so hard to pinpoint one explanation of the cause of psychopathological disorders. Again in OCD reduced serotonin is likely to be a factor in the cause.

Low levels of various neurotransmitters, namely noradrenaline, serotonin and dopamine, which are all under the category of ‘monoamine’ neurotransmitters, have been linked with depression and some forms of anxiety. Interestingly it may be a case that they work together, for example Kety (1975) conducted studies which found that noradrenaline is generally controlled by the level of serotonin, however when the level of serotonin is low, the levels of noradrenaline fluctuate as they are less controlled, dopamine is also involved.

Noradrenaline is associated with physiological arousal in general. It has been found in individuals who have low levels of the neurotransmitter that they are more likely to develop periods of acute depression and on the contrary, high levels have been linked to mania. However much research has contradicted the ‘cateholamine hypothesis’ (the hypothesis into noradrenaline as a factor in depression). While there is often a relationship between the levels of noradrenaline and depression, we also need to consider that the neurotransmitter does not affect everyone in the same way, for example in studies it has been found that in some depressed patients there is no depletion of the neurotransmitter at all.

Serotonin is linked to arousal and sleep, generally increases in serotonin reduce arousal. It is known that serotonin is greatly linked with mood and that levels of serotonin in the brain and associated with aggression. Methylendioxymethamphetamine or MDMA, which may be more familiarly known as the pure form of the drug ecstasy is said to have a euphoric effect on a persons mood, often creating feelings of love and generosity to people around them, even strangers. It works by increasing the amount of serotonin released by neurons in the brain. So it is logical to assume that when our body becomes worse at controlling the levels of serotonin in the body, it could lead to mood disturbance which could link to depression.

Drug treatment for depression and anxiety

Anti-depressants are a common way of treating the symptoms depression and anxiety. There are a range of different drugs used to treat different symptoms, and some drugs may suit some individuals better than others. Treatment is based on altering the levels of neurotransmitters such as serotonin and noradrenaline in the brain. This is because these neurotransmitters regulate the things like sleep patterns, emotions, sex drive and reaction to stress, and there is evidence to suggest that they are involved in the onset of depression.

The first type of drugs used for treating depression was tricyclics, which are still used today. They work by inhibiting the the re-uptake of serotonin and noradrenaline in the brain, meaning that the availability of the neurotransmitters is increased. Therefor there is more serotonin and noradrenaline in the neuron communication system (the system in your body in which signals are transported and received via neurons) so messages can be intensified, ie more serotonin used to stimulate the neurons.

MAOI’s are another useful anti-depressant. They work by inhibiting the production of an enzyme called monoamine oxidase. Monoamine oxidase is produced in the body, and its function is to break down neurotransmitters; so a lack of monoamine oxidase results in fewer neurotransmitters being broken down, and therefor the neurotransmitters (such as again noradrenaline and serotonin) are more abundant in the body, and have a greater effect. MAOI’s are widely used, combating many forms of anxiety, and depression.

Further development of drugs include SSRI’s, or selective serotonin re-uptake inhibitors, which as the name suggests, are specific to serotonin. They work in the same way as the tricyclics, ie they stop the pre-synaptic neurone (this is the end of the neuron, which passes an impulse to the start of the next neuron, ie the post synaptic neuron; you may also be familiar with the term pre/post synaptic membrane, which simply refers to the barrier separating the inside contents from the outside of the membrane, it might be useful to think of the membrane its ‘skin’) from re up taking the serotonin, meaning that it can keep acting on the post synaptic neuron.

Beta blockers are more often used in anxiety, particularly in times of stress, the body goes into a state of shock, which may be referred to as ‘the fight or flight’ response, the body reacts by increasing the amount of adrenaline circulating in the blood, increasing blood pressure so that bloody can be passed to the bodies cells more efficiently, as oxygen is in high demand and must be delivered to these bodily cells, heart rate is also increased, in order to pump blood around the body more efficiently. Beta blockers work by reducing these symptoms, they lower the heart rate and reduce blood pressure, and they work relatively quickly, meaning that they are particularly helpful in a stressful situation, making the user feel calmer, and more at ease.

Drug therapy is often shown effective in depression. Generally it is found that tricyclics produce fewer side effects, and are more effective than MAOI’s. SSRI’s are found to be at least as effective as tricyclics and often show even less side effects; tricyclics have been reported to cause dizziness, blurred vision, dry mouth, and constipation. However SSRI’s are known to react with other prescription drugs, and can also have their own side effects such as reduced sex drive, nausea, insomnia, and excessive sweating.

 Evaluation of drug use anxiety & depression disorders

 As previously mentioned, there is an ongoing problem with side effects in drugs used to treat depression. Common side effects include weight gain/loss, drowsiness, sexual dysfunction among many others. This is a problem as it is often the case that someone suffering from depression or anxiety cannot use drugs to cure or decrease the symptoms of what they are going through. Long term effects of drugs may also be a problem in some cases, which can sometimes be irreversible.

Effectiveness of the drugs used in depression in debatable; one of the major problems with using drugs to treat mental issues is the fact that, treatments can either be curative or palliative. Curative treatments actually solve the underlying problem, ie in depression this could be either psychological, or biological or both. Palliative treatments mean that the symptoms are suppressed, but the actual problem may not be addressed. Drugs are in most cases a palliative treatment, as biological explanations of depression are still in the early stages or development, although depleted levels of some neurotransmitters have been linked with depression, there is not yet any known direct cause, and so we cannot draw a cause-effect relationship, meaning that we can’t prescribe drugs knowing that they will be 100% effective. Studies consistently address this problem, some people may not be affected by drugs at all, and will still be faced with the problems of depression. Healthy lifestyles, where a good diet and moderate exercise are practiced have also been found to produce effects which match the effectiveness of drugs, meaning that symptoms concerned with depression and anxiety, again this questions the effectiveness and appropriateness in the use of drugs to treat anxiety and depression. Consistently in studies it is shown that a combination of therapy and prescription drugs is the best way to target mental disorders as all the areas which we have found to be a factor of depression/anxiety is covered; often it is the case that someone who is suffering has a mixture of both a base of genetic and social development.

Placebo effects occur when someone believes that because they have taken the medication, they will automatically feel better, and so may feel better without the drug even taking effect, trials are often tested for new drugs with two test groups; one with a placebo drug (fake drug) and one with the real thing, it is often the case that people report feeling better because they believe they have taken a drug which has had an effect on their body. An american anaesthetist called Henry Beecher demonstrated this during the second world war, he had ran out out of morphine and instead used salt water to treat patients, who claimed to feel much better. Reliability of the drugs used in therapy is challenged due to placebo effects.

Addiction and tolerance build up to anti-depressants often has to be considered. A build up in tolerance is where because the body is used to drugs being taken to change conditions within the body (reduced serotonin/noradrenaline re up-take, reduced autonomic responses) more may be needed to generate the same effects that they had when they were first taken. Addiction is similar to this as if/when a patient stops taking anti-depressants, they may feel a need to take them again. Although many drug companies claim that there is no resulting physical addiction due to the drugs, the body is still adapted to them, it may be the case that because their body has built up a tolerance, they come off the anti-depressants feeling worse than they did in the first place-it is often shown that if a patient stops taking medication they will often relapse (start feeling the symptoms again) which again questions whether the real problem is being solved. Psychological addiction is also a problem, as individuals may feel that they will not be able to cope without the drugs.

Pharmaceutical companies may often cause problems themselves; there are huge issues surrounding research, as unfortunately it is sometimes the case that manufacturers will not publish results that do not support, or contradict the effects of the drugs they have made. Furthermore, profitability causes issues, as prescription drugs are not available through the NHS, pharmaceutical companies are constantly making profit as people use their products, it is often the case that companies will push their products to seem better than they are, and to make them more widespread to different problems, this can also lead to a problem with over prescription which is described below.

When anti-depressants were first used, the fact that they were cheap, quick and easy provided a lot of potential for them, however ironically this may be a flaw in their use. Often drugs are over prescribed as the symptoms of depression can easily be targeted, however as discussed before it is not clear whether the cause of depression is being considered. Over prescription can also cause resistance in some cases (this is currently a major issue in antibiotic overuse) meaning that some people may develop a resistance to the drug meaning that the drug can no longer affect them, and reduce symptoms, in extreme examples this can pass onto new populations meaning that generations in the future may have become adapted to not feel the effects of drugs at all, meaning that new ones have to be discovered and developed.

Bonnie Pratt February 2013 (disclaimer)