That's what someone asked me on Quora, and here's how I responded:
The truth is that both depression and derealization are actually symptoms of being traumatized.
Here's what's going on: when people experience some sort of acutely stressful or threatening situation (like a car crash, terrorist attack or mugging, for example), OR, when they experience some sort of chronic, ongoing stressful or threatening situation (like being around emotionally abusive people, for example) – they often develop what’s called Post Traumatic Stress Disorder, or PTSD for short.
When the fear of being severely hurt / abused / neglected / is chronic and ongoing (as opposed to a dramatic ‘one-off’ event), then the person is said to have developed something called ‘Complex PTSD’, or C-PTSD, for short.
One of the very common symptoms associated with a PTSD-type response is that the traumatized person starts to feel disconnected from the world around them, as though either it’s not real, or that they aren’t real – that’s the derealization that you’re describing.
The ‘Mohawk’ of Self-Awareness
Physiologically, this is happening because the part of the brain that’s most involved in the body awareness is literally taken off-line by severely traumatic experiences. In his excellent book ‘The Body Keeps the Score’, Bessel Van Der Kolk describes this part of the brain as the ‘mohawk of self-awareness.’
If you take a look at the diagram above, you’ll see the five parts of the brain that are responsible for registering sensations coming in from the outside, and for effectively feeling ‘real’. To quote Van Der Kolk, these five regions are:
“The posterior cingulate…gives us a physical sense of where we are…the insula…relays messages from the viscera to the emotional centres; the parietal lobes which integrate sensory information; and the anterior cingulate, which coordinates emotions and thinking.”
When they did brain-scanning experiments with traumatized people, they found that most of these areas of the brain were completely off-line. The only part that was functioning in any small way was the posterior cingulate, which literally stops you from walking into walls, etc. (BTW, this is also why traumatized people are routinely clumsy and physically awkward.)
So to recap, the parts of the brain that are responsible for sensing the world, and for helping the person orient themselves in their surroundings etc, is usually almost completely shut down traumatized people
Again, this happens to people who have PTSD, and C-PTSD, and most of the people with C-PTSD usually got that way because they experienced chronic abuse and neglect at some point in their lives, very often when they were children.
The Connection to Depression
So now, how is all this connected to depression?
First of all, let’s explain what’s going on from a physiological stand-point.
When people are traumatized and have some sort of PTSD / C-PTSD, that can lead to feelings of derealization (as described above).
When someone is feeling permanently traumatized / shocked / stressed-out at the physiological level, that means that their body’s fight-flight-freeze mechanism is effectively jammed in ‘shock’ mode.
Some traumatized people will react with ‘fight’ to external stimuli that are triggering them – i.e. always irritable, angry, on the defensive, aggressive, in your face.
Others will react with ‘flight’ – i.e. escapism, running away from difficult situations and relationships, tuning-out mentally etc.
Then, there’s the most problematic state of all, which is ‘freeze’. Freeze is what happens when neither fight or flight worked to solve the problem, and the body sends the mind the signal to shut-down and go into a sort of mental ‘stand-by’ mode, where only the most basic systems continue to operate, and the person often spaces-out or disassociates from what the very difficult thing they are experiencing.
‘Freeze’ is effectively clinical depression.
Just to bring this point home, recent research was done that showed that so-called ‘silent’ forms of child abuse like emotional abuse and severe neglect cause depression.
How do you solve the problem?
Anything you do to solve the trauma will positively affect both the derealization and the depression, which are both effectively symptoms of the PTSD / C-PTSD.
Trauma is causing both the depression and the derealization, and once you take care of that at its root, these symptoms – and any others associated with the trauma – will reduce and disappear over time.