In the past couple of months, actor Kangana Ranaut has posted many tweets about depression and mental disorders. While it’s important to talk about mental health, unfortunately, many of Kangana’s tweets have incorrectly represented scientific research or left out important facts.
Here is what science actually says.
- The use of blood tests and brains scans to diagnose mental disorders
While it is true that psychiatrists and psychologists don’t commonly use scans for diagnosis, blood tests are actually very commonly requested. This is to check for hormonal imbalances that could be the underlying cause of depression or any other mental disorder. For example, one commonly checked hormone is thyroid level since it can have an impact on one’s mood and sleep.
As for brain and body scans, many recent studies have found that the brains of those suffering from mental disorders are both structurally and functionally different than those who don’t. These differences can be viewed under various brain imaging techniques. Patients with depression tend to show large volume reductions in frontal regions, especially in the anterior cingulate and orbitofrontal cortex with smaller reductions in the prefrontal cortex of the brain. These areas of the brain are responsible for executive functions such as decision making, planning, and emotion regulation. The prefrontal cortex is also the part of the brain responsible for releasing neurotransmitters such as dopamine, serotonin and norepinephrine.
Furthermore, the hippocampus, the part of the brain that controls for emotions and memory, has been consistently found to be significantly smaller in patients that are depressed. The longer one had been depressed, the more the hippocampus shrunk in size, further limiting memory and emotion functions.
Unfortunately, we haven’t been able to use brain scans for diagnosis yet, but research is ongoing and hopefully, we will soon be able to use them to diagnose and create specific treatment plans.
2. The role of environmental factors on Mental Health
It’s true that stressful life events can contribute to the development of mental disorders, however, biological or genetic factors seem to have a more significant impact.
It’s quite well known that biological factors such as differences in neurotransmitters and hormone levels are known to contribute to mental illness. A lesser known fact about mental disorders is that their heritability is very high, in some cases much higher than physical illness. Heritability refers to the statistic that helps us understand how much of a particular characteristic or illness is usually a result of ‘nature’ in comparison to ‘nurture’ The heritability of depression is known to be about 48% – 70%. To give context to how high this is, the heritability of obesity is known to have the same range (40%-70%), blood pressure much lower (24.4% – 30.3%) and height is a little higher (89% -93%).
This means that approximately 90% of the time, one’s height is a result of genetic factors. Environmental factors such as nutrition, and exercise can also contribute to one’s height, however, when we look at a population, about 89%-93% people are of a certain height due to genetic factors. Only about 10% of a population’s height is not determined by ‘nature’ but instead determined by ‘nurture’. Similarly, at least 48% of a population experiences depression due to genetic factors, and in different populations this number could go up to as high as 70%.
The reason that the heritability of mental disorders function on a range is because mental disorders are a polygenic trait, meaning that not just one gene, but multiple genes determines whether one will develop a mental disorder. However, there is one gene mutation that has been found to have significant correlation with the onset of various mental disorders. The gene is called MTHFR and it seems to be involved in the production of an essential enzyme – methylenetetrahydrofolate reductase. People with this gene mutation have been found to have a much higher risk of developing mental disorders.
Genetic predisposition and environmental factors together determine how vulnerable one is to mental disorders. To understand this interaction, let’s look at the example of Phenylketonuria (PKU). Phenylketonuria is a genetic disorder that results in a defect in the gene that helps create the enzyme needed to break down the amino acid phenylalanine. Without the enzyme necessary to process phenylalanine, a dangerous buildup often leads to intellectual disability, seizures, behavioral problems, and mental disorders. If provided with a diet that limits phenylalanine, these can be prevented.
Similarly, in the case of depression, genetic factors can cause one to be more vulnerable and sensitive to stress the same way PKU makes one more vulnerable to phenylalanine. In the case of no genetic risk involved, one is either not susceptible to mental disorders at all or much more resilient to stressful life events in comparison to those who are genetically predisposed. Overall, how vulnerable or resilient one is in the face of stressful life events, seems to be determined by our genes.
This is not to say that environmental factors alone cannot cause depression. However, resilience to mental health disorder does seem to be more correlated with your genes than a healthy environment, although a healthy environment can increase or lessen your resilience.
3. The Relationship between Depression and Drug Abuse
The relationship between depression and substance abuse is bi-directional. A large number of people who suffer from depression never seek medical treatment and instead, use alcohol and drugs to self-soothe. At the same time, those who struggle with addiction are much more likely to develop depression since alcohol and drugs tend to alter brain chemicals, possibly making one more susceptible to mental disorders. With that said, a large number of times, mental health disorders usually occur before substance abuse and addiction.
However, an interesting point to note is that addiction too, is quite heritable. Although everyone has the potential to become an addict, some people are more vulnerable than others. Studies show that if a parent has a drug or alcohol addiction, the chances of their child developing an addiction is 8 times greater.
Adoption studies are commonly used to study whether nature or nurture is more important for the development of a particular characteristic or behaviour. Studies have found that among adopted children, those that have biological parents with a history of drug abuse, are much more likely to engage in substance abuse themselves. On the other hand, the risk of drug abuse in adopted children raised by a parent that had a history of drug abuse was not significantly increased, suggesting that genetic factors play a greater role in determining the likelihood of drug abuse and addiction. Similarly, twin studies have found that if an identical twin (shares a 100% of your DNA) has a history of addiction, you have a higher probability of developing an addiction, than if you had a fraternal twin (shares 50% of your DNA) with a history of addiction.
Therefore, although it’s true that one’s depression may be a result of substance abuse, it is unfair to villainize any of the two. Yes, our actions and environment does influence the development of both behaviours, but given that both conditions seem to be heavily dependent on genetic predispositions, it’s important that we spend more time educating ourselves and finding efficient ways to prevent addiction and mental health, instead of stigmatizing them even more.
Aradhya is a student of Psychology, Biology and Media Studies at Ashoka University.
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