Childhood Depression and the Brain: Hippocampus and Prefrontal Cortex

This is a continuation of my posts about the biology of childhood depression.  I’m writing about the brain in very easy to understand language.  I’ve written about neurotransmitters, the HPA axis and cortisol in my previous posts.  Now I’d like to talk about the hippocampus then the prefrontal cortex.  They’re not as complicated as they sound.  I’m giving very basic descriptions that most anyone can understand.

The hippocampus is a part of the brain that helps form new memories of experiences and events in our lives like what happened, where it happened and when it happened but also memories about how the experiences and events made us feel and how those emotions affected us.

I wrote about cortisol a.k.a. the stress hormone in an earlier post.  Traumatic, depressive or stressful experiences and events are processed through the hippocampus then sent to the HPA axis and cortisol is released.  If too much cortisol is released over time, the cortisol can kill off neurons in the hippocampus and stop the hippocampus from making new neurons. 

I wrote about neurons and neurotransmitters in a previous post.  When neurons are killed and new neurons can’t be made the hippocampus can become smaller.  Studies have shown the hippocampus can be reduced as much as 20% in some depressed individuals. 

A smaller hippocampus can make it more difficult for a child or anyone to process and deal with trauma and traumatic or depressive events and memories.  This can cause more stress which would increase cortisol levels even more and that can cause the hippocampus to become smaller.  It seems like a vicious cycle. 

A smaller hippocampus can also make it more difficult for children, adolescents and adults to think, reason, understand and remember.  This could explain some of the cognitive issues depressed people can have.  On a more positive note; daily exercise, therapy, and anti-depressants can reverse some of the damage to the hippocampus by helping the hippocampus make new neurons.  So there is hope. 

Now I’d like to talk about the part of the brain called the prefrontal cortex.  The prefrontal cortex helps us process, interpret and regulate how we feel.  It helps us see relationships between events.  It helps us interpret events and make predictions about the future consequences of our actions.  It also helps to regulate stress by inhibiting the HPA axis and reducing cortisol levels. 

When the prefrontal cortex is working the way it is supposed too it can help regulate negative emotions but when it’s not working right it may make the HPA axis hyperactive and too much cortisol may be released. 

Too much cortisol over a period of time can reduce activity in the prefrontal cortex.  This reduction in activity can affect our ability to process and regulate our emotions. 

The prefrontal cortex is divided into two halves.  The left side helps establish positive feelings and may inhibit negative emotions.  The right half establishes negative memories.  The left half seems to be more affected by cortisol, reducing activity in the prefrontal cortex and possibly reducing our ability to feel positive emotions and inhibit negative emotions. 

One part of the prefrontal cortex called the ventromedial prefrontal cortex is the key center for processing and regulating emotions.  Studies have shown that the ventromedial prefrontal cortex is thinner in children who began suffering from depression during their pre-school years.  This may show that the prefrontal cortex could be implicated in depression early in a child’s brain development.  It helps parents know and understand that depressed children aren’t lazy or mean or difficult.  They have an actual biologically based disorder. 

Depression and anxiety are based in the brain like many psychiatric disorders but with therapy, exercise and sometimes medication children can overcome their pain and live a relatively normal life.   

In my next post I will talk about the part of the brain called the amygdala.