• Addiction – a Disease or Weak Will?

    MRI scan showing effects of addiction

    Can we blame the addict, or should we pity her?

    Is addiction a disease, or is it due to a weakness of character?

     

    The simple answer is that addiction is now considered to be a disease state; but to make it more complex – we like it that way, don’t we? –  weak will adds to the problems.

     

     

    Are we responsible for all our behaviors?

    The law takes its own position on this – but medical science has progressively eroded our confidence on Independent and Free will – many now believe that we are what our hormones – or brain chemicals – make us.

    Addiction is now considered to be a chronic brain disorder  that is initiated by the drug itself; imaging studies have revealed that prolonged and consistent use of drugs of abuse – be it heroin, cocaine, crystal meth, or alcohol – initiates and maintains changes in the internal circuitry of the brain which affects memory, thinking, concentration, behavior control, and decision – making. All these changes then somehow lead to the compulsive and destructive behavior characteristic of the condition.

    cocaine-addiction-rehabilitation-460x305

    Cocaine sniffing is popular among elites as well

    Do circumstances or social factors play any role?

    Addiction cannot be considered to be a purely biological or a purely environmental problem – it is a mixture of both.

    That means that certain personality traits of the individual make them prone to compulsive,  repetitive, and mind-less behavior. Such people are also prone to suggestions, have a need to conform to a group or to their circle, and may have various reasons to start taking drugs along with their friends. These are environmental factors.

    The Pleasure Priniciple

    In the initial stages, taking the drug gives the person pleasure, called ‘a high’ in street slang, and ‘reward‘ in psychological parlance.

    IDU

    Intravenous Drug Use is possibly the riskiest

    Reinforcers are agents which increase the possibility of a particular sequence of events happening in the brain circuits.

    Natural reinforcers which produce the reward effect include sex and food; a drug has a greater effect as a reinforcer than any natural reinforcer, which is why drug-addicts give up sex and food in favor of the drug of abuse.

    Changes with long-term abuse of drugs

    On the other hand, repeated intake of the drug alters critical areas in the brain such that the individual suffers severe reactions – called withdrawal symptoms – if the drug is not taken; this initiates the vicious cycle of addiction.

    Drug addiction before and after images

    Drug addiction before and after images in Crystal Meth user

    These changes have been documented in imaging studies, and much is now understood about the exact areas in which these changes occur. Based on this, several new therapeutic techniques are being evaluated.

    For example, nicotine patches and e-cigarettes are helpful in reducing addiction to tobacco. Naloxone is used not only for morphine/heroin, but is also useful in alcohol addiction.

    Chronic use of drugs of abuse result in changes in the protein and RNA within the cells, and that is one reason why the effects are long-lasting, even after the drug intake has stopped; this is the critical phase when the individual is at risk of relapsing to addict behavior.

    Do genes have a role to play in Addiction?

    Genetic factors contribute to the vulnerability to developing drug addictions and the different response to treatment for addiction.

    The OPRM1 gene has been studied the most in this respect. One particular variant of the gene which makes the person prone to addiction (called the 118 G allele) is most common in Asian populations (40%–50%), has moderate frequency in European populations (15%–30%), and has very low prevalence in African populations.

    The 118G allele has been associated with dependence to opium-like substances as well as to alcohol and other substances, reduced hormonal response to stress, and reduced benefit from morphine and other opiates.

    Carriers of the 118G allele also show an elevated sensitivity to pain. Other genes are commoner in the other races.

    Does this mean addiction is inherited?

    When certain diseases are seen more frequently in some families, the temptation is to blame it on genes; this is the great Nature versus Nurture debate.

    The basic point is that a family shares not only genes, but a common environment.

    The currently accepted model here is that genes do play a very important role in expression of diseases, especially those affecting our minds, psychology, or behavior; but these genes express themselves more depending on the environmental factors.

    This means that it’s not enough for an individual to have the genes; if the parents model certain kinds of behavior for their children, then those who have the relevant genes are more likely to express similar behaviors.

    So the blame is not entirely on the genes, but also on our own behavior!

    Some Fundamentals of Brain neuronal circuits

     

    A neuron

    A Neuron has a cell body and some projections – called dendrites and a single Axon

    As we all know, the brain is made up of nerve cells, or neurons.

    Neurons connect with each other through their axons and dendrites, and communicate with each other across this connection called the SYNAPSE.

    This communication involves transmission of very weak electrical currents. This electrical current differs from the electricity we use in our daily life – because it is related to chemical changes – it is an electrochemical phenomenon.

    Spatial memory circuit

    Proposed map showing connections in the Medial Temporal lobe, explaining the circuit which plays a central role in spatial memory (an example of a circuit in the brain)

    Information is transferred across the synapse through special molecules called neurotransmitters; examples include adrenaline (epinephrine), dopamine, serotonin, etc.

    The hippocampo-entorhinal circuit

    The hippocampo-entorhinal circuit – and illustrative image; the hippocampus receives inputs from layers 2 and 3 of the entorhinal cortex and sends output to layer 5 of the entorhinal cortex

    Neurons combine together to form circuits; based on their connections, these circuits play specialized roles.

    Learning new skills is dependent on reinforcing activity within special circuits. As we practice more and more to develop a skill, activity in a particular circuit becomes progressively more efficient. This concept of circuit is important to understand addiction.

    Drug addiction involves multiple brain circuits

    A network of four brain circuits are involved in drug abuse and addiction: (a) reward, located in the nucleus accumbens (NAc) and the ventral pallidum; (b) motivation/drive, located in the orbitofrontal cortex (OFC) and the subcallosal cortex; (c) memory and learning, located in the amygdala and the hippocampus; and (d) control, located in the prefrontal cortex and the anterior cingulated gyrus (CG).

    Don’t worry if the anatomical names here don’t mean anything to you; the important point is that reward, motivation/drive, memory and learning, as well as (executive) control have special circuits; activity within a circuit is either suppressed or enhanced in a given situation.

    Findings on Imaging Studies

    Imaging studies – such as PET and fMRI have revealed neurochemical and functional changes in the brains of drug-addicted subjects that provide new insights into the mechanisms underlying addiction.

    Crystal Meth user

    An example of the kind of effects Crystal Meth has on the face of the user

    Neurochemical studies using these high-end imaging technologies have shown that increases in a major neurotransmitter in the brain called dopamine are associated with the reinforcing effects of drugs of abuse.

    Cingulate Cortex

    The Anterior Cingulate Cortex becomes hypo active during chronic addiction

    After chronic drug abuse and during withdrawal, brain dopamine function is markedly decreased; this decrease leads to dysfunction of parts of the fore-brain (prefrontal regions including orbitofrontal cortex and cingulate gyrus), which have much to do with our capacity to think, judge, and take decisions.

    Functional imaging studies have shown that during drug intoxication, or during craving, these same (frontal) regions become activated along with other areas which are related to reward, motivation, memory, and cognitive control.

    Model for Addiction

    Based on these findings and our understanding of brain neuronal circuits, a model for understanding addiction has been proposed.

    As per this model, addiction is a state initiated by the qualitatively different and larger reward value of the drug.   This triggers a series of adaptations in the reward, motivation/drive, memory, and control circuits of the brain.

    Activation of reward pathway by drugs

    Activation of reward pathway by drugs

    These changes result in an enhanced and permanent value for the drug, and in the loss of inhibitory control (from the forebrain), favoring the emergence of compulsive drug administration.

    Implications of this model

    The model has treatment implications, for it suggests strategies to combat drug addiction — specifically:

    (a) Interventions to decrease the rewarding value of drugs, such as pharmacological treatments that interfere with the drug’s reinforcing effects as well as treatments that make the effects unpleasant;

    (b) Interventions to increase the value of nondrug reinforcers, such as pharmacological and behavioral treatments that increase sensitivity to natural reinforcers and establish alternative reinforcing behaviors;

    (c) Interventions to weaken learned drug responses,

    (d) Interventions to strengthen inhibition, such as cognitive therapy.

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