Q: How does childhood trauma cause addiction?
Basic biology: children who were neglected or abused did not receive the proper conditions for their nervous systems to develop properly. Because of their volatile caregiver environment, they experience significantly higher volumes of the stress hormone cortisol on a day-to-day basis. If left unaddressed, this carries on into adulthood. In contrast, children who had proper developmental conditions (safe, secure connection to their caregiver) develop a healthy internal hormone regulatory system, and therefore don't experience stress to the same degree as abused or neglected individuals do. Addiction is simply the evolutionary act of seeking a tool to reduce that stress. All addictive substances release biophysically healing (cortisol reducing) neuro-chemicals called endorphins. The more stress is experienced by the body, the more endorphin activity is required to soothe the body. The more that cortisol levels skyrocket, the more the nervous system automates endorphin seeking behaviours.
So why does abuse cause so much lasting stress? When a child is in those crucial developmental years that happen before the age of two, a child's brain and body are exceptionally vulnerable to external circumstances. This is evolutionary so that we adapt to our surroundings, learning to keep us safe from harm before anything else. We learn to fear what hurt us so that our bodies react faster to get us out of the way.
To understand this, picture a red-hot stove iron. If you touch it and it burns you - you feel excruciating pain. Your senses - like the sight of the red glow, the sound of the burner - are heightened. They get stored in your limbic system (part of your body's nervous system). So the next time you see your arm near the red hot stove iron, or hear the burner flick on when your hand is on it, your nervous system reacts more immediately than your mind can, in order to jerk your arm out of the way fast. The limbic system stores these sensory memories longer and more deeply than your conscious mind, so that your contemplative, reflective, calculating, longer-to-process, thought system (the brain) is bypassed. The limbic system can then assure that the body reacts faster just at the mere perception of the hot stove iron being close, without having to sit and reflect on whether or not the red stove is hot - your body just knows (before the brain does!)
So how does this relate to Trauma? While a child's nervous system is developing, if their parent of caregiver hits them every time they ask for something they need (like food or a hug), in response to that pain their limbic system stores the sight of a hand being raised, or the loud shout of an angry parent, within its limbic (central nervous) system so that the body can react fast to get out of harm's way. It does this by: releasing high dosages of the stress hormone cortisol and the panic/motivator chemical adrenaline, sending the blood from the brain to arms and legs so that the child can move out of the way as fast as it can. (This is often called "fight or flight" syndrome.) So then later on down the road in that child's life, if they have been struck repeatedly, their nervous system will be set up to alert the body to react even at the mere sight of an arm being raised, or the sound of an angry voice yelling near them. They are on high alert constantly due to an over-adaptation of this very basic survival mechanism.
Now when you bring in the effects that highly addictive substances (like heroin, cocaine, alcohol, cigarettes, high-fat, high-sugar foods) all have in common, it's understandable why so many children who were abused become compulsively fixated on obtaining and using them. The common thread in these addictive substances? The are all extremely efficient tools for the release of endorphins. Endorphins are bio-chemicals that upon release, activate the reward centre of the brain, soothe stress and anxiety (reduce cortisol levels), momentarily heal pain, and give humans that warm, cozy, "ahhh" feeling - similar to a hug from someone you love. So because children who were abused endure significantly higher levels of stress (the "fight or flight" response and spikes of cortisol are induced far more often) that individual has a tough time dealing with even the smallest of daily tasks and responsibilities that revolve around the emotions of others, and constantly need to reach for something to relieve that stress and the long-term physical pain that notoriously comes from it.
Q: But it happened so long ago, why can't they just get over it?
Again, it's a nervous system response, not a conscious thought response to that childhood trauma. In fact, most adults who were abused as children will tell you, "So what, I'm over it, who cares." while they emit a tough-demeanour and a who cares attitude if ever asked about their childhoods. This is because we have been reprimanding sadness, vulnerability, and emotional individuals for centuries - they are deemed undesirables in society and the vulnerable are the first to pick up on that. No one wants to be the victim of abuse so they often block it out, and get tough. But it's their adaptive nature that responds regardless of what they tell themselves in their conscious minds, and to others around them. It takes a lot more than 'acting' tough to work out the limbic and central nervous system's autonomous response to the perception of pain. A lot of times they feel angry that they can't seem to control themselves in the face of whatever drug or drink that controls their lives, but they rarely want to talk about what happened to them as children because they've 'put that behind them'.
Even if a child who suffered through abuse in their developmental stages does find themselves in a position where they have done 'everything right' and avoided smoking, drinking, and drugs - all the things that we've always been told will ruin your life - they will still find themselves engaging over compulsively in other legal things that have the same effects of lighting up the reward center of the brain. Say they can't stop eating highly processed foods, having sex with too many people, overdoing some extreme sports, shopping out of control even when they are in extreme debt. The stress of their overexposure to pain in those developmental years will be too much to handle on their own and if not addressed they will constantly seek a reward to reduce the harm from so many environmental stressors.
To talk a bit more about environmental stressors, contrast the child who was abused with the child who whenever they asked for a second helping of oatmeal, or an extra hug or blanket before bed, the parent responded with a warm, genuine smile and eye contact, and said, "Sure son, come with me to the kitchen for another scoop" or placed their newspaper down and said, "Of course you can, come in for a hug." The kid will not have a build in nervous system reaction to asking for something, and will feel confident that their needs will always be met. This child will grow up into an adult who will be able to ask for a raise for the hard work they've done, while the child who has a maladapted nervous system will be shoot with stress and anxiety when they even just think about asking for a raise. In fact, it will become easier for them to avoid an authoritative boss figure all-together. Or if they are in a position where they have to be under the pressure and perception of abuse that comes from a demanding boss, they will find themselves compulsively engaging in something to reduce that very visceral fear and over-reaction of the body's fight or flight syndrome after the perception of any reminder of that initial pain from the developmental years.
Q: I never hit or physically abused my child, so why are they addicted?
Unfortunately, before the science confirmed otherwise, parents thought they were doing a wonderful job if they were just making sure their children weren't physically harmed. But the research now shows that neglect is a silent killer. Most parents in the West don't understand how much their infants need physical touch, eye-contact, and a soothing voice. These things - once considered to be emotional luxuries - are in fact required for the infant's nervous system and bio-chemical regulation to develop properly. Psychologist John Bowlby called this developing a secure attachment bond. Secure attachment bonds assure that the child develops an armour against stress from rejection, loneliness, and other 'emotional' pain that physically harms the body in the same way that falling and being hit does - you just can't see it. In fact so-called 'emotional' pain can be so harmful to the body, that Tylenol - a known pain killer - reacts on the same centres of the brain for both physical and emotional pain.
Q: But I was abused and I'm not addicted to anything. Why's that?
The most effective way to reverse the limbic system's overreactive response to environmental stressors or perceptions of potential pain, is to unlearn it by being around others who are warm, open, genuine, understanding, and kind. Your limbic system starts to store these memories of laughter and affection on top of the physical pain in response to something like a loud voice. Neurologists have found that you can't 'unlearn' old patterns of addictive behaviours, but that you can rewire the brain by laying new patterns over old ones. Some people are fortunate to have found a strong social community to swoop in and teach the abused child's nervous system that their environment is, in fact, safe and void of harmful aggressors. Due to their safe and secure surroundings, these people develop an armour and a resilience against external stimulants that would have otherwise triggered the flight or fight response or induced the extreme cortisol response left over from the PTSD of childhood abuse.