Therapy Analysis - Drug addiction
Rewarding behaviour, but at what cost?
The neurochemistry associated with drug use and addiction is complex and involves many interrelated pathways. However, all drugs of addiction have one thing in common - they produce a sensation in the user that is pleasurable, the so-called 'high'. The common factor for all abused drugs is that they stimulate the mesolimbic reward pathway in the brain, with the neurotransmitter dopamine a key element. This chemical is released naturally by the brain in response to stimuli such as food or sex, but it is also released by drugs of abuse. Substances which activate the reward pathway are positively reinforcing - that is to say, the pleasurable effects experienced by the user when the pathway is stimulated drives them to repeat the experience. It is when this reinforcement becomes aberrant and the user engages in compulsive drugseeking behaviour, that true addiction sets in. To compound the problem, tolerance to the effects of a drug builds up over time, often by the reduction in dopamine receptors on the dendrites of neurons. The user therefore requires more and more to achieve the desired effects and when the drug is no longer available, such as when an effort is made to quit, an addict will go through a period of withdrawal. The overstimulated reward pathway is no longer active and a dysphoric state ensues. This often leads to relapse.
...Perhaps the most addictive of drugs is cocaine, which is linked to not only the dopamine pathway of the midbrain, but also the glutamate and the noradrenaline pathway...The involvement of neurotransmitters has been explored scientifically throughout the last century and many scientists now implicate the neurotransmitters 5- HT (serotonin), noradrenaline and glutamate in the process of addiction. Perhaps the most addictive of drugs is cocaine, which is linked to not only the dopamine pathway of the midbrain, but also the glutamate and the noradrenaline pathway, which activates the fight-or-flight response triggering an increase in heart rate, blood pressure, body temperature and dilation of the pupils. Cocaine binds to the dopamine reuptake transporters, thus blocking functionality and as a result, dopamine levels increase in the synapse, so the receiving neuron is continuously stimulated - this constant firing of the neurons leads to a feeling of euphoria. Another factor in the reinforcement of cocaine use lies in the fact that after cocaine administration, dopamine levels fall significantly below normal, pre-consumption levels. The user therefore feels a "low", and the immediate response to alleviate this low is to consume more cocaine to raise the level once again. Being a key player in memory regulation, it is theorized that glutamate is directly linked to trigger memories that lead to relapse. In one study, researchers stimulated a memory-related brain area that is rich with glutamate, which caused rats weaned off of cocaine to frantically press a lever that previously dispensed the drug. In essence it caused a relapse, and blocking glutamate activity subsequently blocked the response.
Generally, the neurochemistry of addiction is heavily theorized and not yet fully understood, and the addictive nature of drugs varies from substance to substance, and from individual to individual. Owing to their neurochemical effects, drugs such as codeine or alcohol, typically require many more exposures to addict their users than drugs such as heroin or cocaine. Likewise, a person who is psychologically or genetically predisposed to addiction is much more likely to suffer from it. There are anecdotal reports of psychological addiction to recreational stimulants such as MDMA (ecstasy) and a dissociative psychedelic ketamine, but it is thought that pills sold on the street as 'ecstasy' often contain adulterants, which may be the addictive compound.
