Depression genes activated by childhood trauma – stay turned-on and passed-on to your children: Exposure to extreme poverty, abuse, drug dependency and violence as a child can activate genetic systems which lead to depression later in life. Once activated these epigenetic processes stay that way and can even be passed on to your offspring. New research describes the mechanisms involved and raises hope for new approaches for dealing with serious mental conditions.
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We all inherit a double set of genes from our parents, one set from our father via his sperm and the other set from our mother through her egg. These two sets combine in what is our first cell which then multiplies to create the billions of human cells that make up our body. In this way every human cell in our body starts off with the same two sets of genes (except for when we make our own sperm or egg cells – here our double set is halved so the cycle can continue when they meet up to create our children).
You inherit genes from your parents through the information coded in DNA – an incredibly long molecule that the genes are made from. You can think of DNA as a string of thousands of genes arranged rather like the beads on a necklace – each bead containing the information to manufacture a molecular component of the machinery that makes up our body. More recently we have discovered that these genes can be tagged or marked by adding a small molecular methyl group. One of the purposes of this methyl tagging process is to turn off the gene.
Turning off genes is important because not all of our genes are needed in every cell. For example the cells which make up the lens of an eye do not need to be able to produce the enamel which is normally found in teeth. However since all cells contain the same set of genes (in their ‘necklace’) they all have the instructions to make every component needed throughout the body. So to avoid every cell producing loads of stuff which would be useless for its specific job many of its genes are turned off as the body develops from the original single cell. A bit of the DNA molecule that is close to the gene has the ‘don’t make me‘ methyl tag attached to it.
When a gene is shut down using a methyl tag it usually stays shut down and even if the cell multiplies this gene can stay shut down (so all the new cells produced when this cell divides also get a methyl tag attached at the correct spot). This means that, early in our development, once eye cells have been tagged to not produce tooth enamel they and their offspring cells continue to have this enamel gene turned off. If this didn’t happen we might end up with teeth growing in the middle of our eyes!
Methyl tagging doesn’t just turn off ‘construction’ genes like those to make enamel or eye lens material. It also works on important messenger molecules that play a role maintaining our balanced psychological state. One of these messenger molecules (made by the gene SLC6A4) is involved in transporting the ‘happiness’ molecule serotonin which stimulates the nerve cells in our body (and importantly in our mind). If the SLC6A4 gene gets turned off using a methyl tag it will not be produced and can’t be involved in telling our nerve cells (and our mind) when happy times have arrived.
What do we mean by happy times? Well serotonin is produced in the gut when a big delicious meal has just landed on the table in front of us. It tells the gut muscles to start contracting so the food will move quickly through our digestive system and we can get the benefit of all those yummy nutrients. It also warns other important parts of the body ‘get ready – nosh is on the way’.
Serotonin also helps create a general psychological feeling of well being. This is important in evolution – it lets an animal know that tasty meals are good and should be consumed as often as possible. That’s why eating can make us happy. Problems preventing serotonin transport in the body have been associated with anxiety and depression – this is why you can think of it as the happiness molecule.
Recently the turning-off of the serotonin transportation gene SLC6A4 by methyl tagging has been linked to increased incidence of depression. Not surprisingly if you can’t use the happiness molecule serotonin you feel depressed. The levels of methyl tagging have been found to be increased when children had been subject to traumas such as childhood abuse or after they experience extreme levels of poverty (low socio-economic status). Once tagged these genes stayed tagged preventing the transport of serotonin which was associated with an increased incidence of anxiety, depression and related disorders later in life.
Last week research was published linking an increased in tendency towards later depression with experiences of lower socio-economic ‘stress’ in a group of 132 adolescent children (Molecular Psychiatry 24th May 2016: , &
This means that although a child may have a full complement of all the genes necessary for a happy and mentally balanced life some of these genes may actually be turned off permanently through poverty or some other trauma in childhood. The turning off may even occur to the DNA of the child’s parents causing the child to inherit its parents’ tendency towards depression. This could help to explain why some psychological symptoms like alcoholism, drug dependency, obsessive compulsive or anxiety related personality disorders appear to have a hereditary component.
I personally find this an exciting development – we are reaching a point with molecular biology where the chemical basis of clinical problems related to the mind and human psychology are starting to be understood. Understanding how conditions in a person’s environment or inherited from their parents are chemically linked to mental problem could help provide us with tools to treat some very serious psychological conditions.
Meanwhile on a slightly lighter note – Tryptophan, a chemical the body uses to manufacture the happiness molecule serotonin, is found in high levels in 85% cocoa chocolate (so is serotonin but sadly it can not cross our blood-brain barrier whereas tryptophan can). So after enduring all this scientific stuff why not treat yourself to some pre-emptive anti-depression therapy. Time to open up the chocolate!
If you found this article interesting please consider taking a look at some of his other recent reports on similar subjects.
Just click on the titles below:
…starting with some more serious stuff:
and here are some fun related articles:
You can also find some of my more humorous reports in the Alpine Press section of this site using the link here.