BIOLOGICAL BASIS OF ADDICTIONS PSY292 ADDICTIONS Disease model of addiction •Created in mid 20th century by Elvin Morton Jellinek •Addiction comes from underlying disease processes •The curve of progression and recovery • Disease model of addiction •At first, these processes were not understood. But it was assumed it is 1) brain disease and with 2) genetic susceptibility •Addicted person is a victim of this disease - it is not chosen and it is not an act of free will •Loss of control & craving as the common processes in addictions •Consumption of the substance causes craving for further dozes (through at first unknown psychological and neurological mechanism) • Disease model of addiction •Since the person is ill and suffering, he/she should be subject of medical treatment •Treatment was based on management of medical complications (stomach ulcer, liver disease,…) and raising patient health education – supervision of a physician •Therapy-like approach heavily influenced by 12 step program and 12-step programs take ideological support from scientific approach of disease model • Disease model of addiction •Addiction as a primary disease – addiction is not understood a result of another condition (other psychiatric condition, stress,…) but rather their cause •Addiction as a progressive disease - addiction is understood as a disease that has its course: 1) adaptive stage - increasing tolerance 2) dependent stage - withdrawal and maintenance usage 3) deterioration stage - resulting into major health and social problems •Addiction as a chronic disease – addiction is understood as a disease that will never disappear and the person will never be fully cured. Thus complete sobriety is the only way Disease model of addiction - pros •Big leap in knowledge, new research •Removes stigma from suffering people •The classic disease model is still very simple to be understood by general public •When addiction became a disease (alcoholism as disease was acknowledged by American Medical Association in 1954) the help became more accessible • Disease model of addiction - cons •Despite huge advancement in knowledge, it was only poorly incorporated into this model. E.g. proofed usefulness of light substance taking contradicts chronic disease; natural remission and maturing out contradicts progressive disease; much stronger environmental factors contradict primary disease •Ignoring context - too little emphasis on psychological and social factors •The treatment method, although advancement at the beginning, is way behind treatments based on psychological and social models • Physical dependency theory •By suing the substance, the person can gradually develop a physical dependence •Physical dependence is a condition in which the person needs the substance otherwise suffers from various withdrawal symptoms •This theory assumes that addiction = physical dependence •NOT proved – many substances do not create physical dependence nor physical withdrawal symptoms. Many addicts return to addiction after period of treatment in which they were detoxified •Avoiding negative effects plays a role, however, more crucial proofed to be the pleasure-seeking • It is about (anticipated) pleasure •Positive-incentive theory - all drugs have pleasurable effects. Drug taking is more about getting the positive effects rather than about removing the negative effect •Positive-incentive value is usually much higher than hedonic value = anticipated pleasure is much higher than actual pleasure •Incentive-sensitization theory – repeated exposure to potentially addictive drugs leads to various changes in brain. The most important is sensitization = hypersensitivity to the incentive motivational effects of drugs and drug-associated stimuli that creates pathological wanting. •Addiction is not about the drug effect, it is about the anticipation of the effect. Addiction is motivation disorder Intracranial self-stimulation http://www.cerebromente.org.br/n18/history/self-stimulation.jpg (8th Edition) John P.J. Pinel-Biopsychology-Pearson (2010).pdf - Adobe Acrobat Reader DC (8th Edition) John P.J. Pinel-Biopsychology-Pearson (2010).pdf - Adobe Acrobat Reader DC Mesolimbic dopamine pathway •Regulates motivation cognition and behavior and reinforcement learning – e.g. regulates behaviours related to food, drinks, safety, sex • •Primary neurotransmitter – dopamine • •The mesolimbic pathway connects the Ventral Tagmental Area near brainstem to the Nucleus Accumbens and to the Prefrontal Cortex. Important role plays amygdala and hippocampus • • Mesolimbic pathway and addiction •In animals, drugs self-administered to nucleus accumbens had stronger effect and were preferred. It correlated with increase on dopamine release •All drugs affect dopamine functions. Many drugs work as direct dopamine agonists while the rest of drugs have indirect effect •Brain imaging technics showed massive dopamine involvement in nucleus accumbens. They also showed decrease of dopamine D2 receptors availability in addicts leading to increasing tolerance •Mesolimbic pathway gradually sticks to the addiction object to which it is hypersensitive while under sensitive to other stimuli – highjacked brain • •https://www.youtube.com/watch?v=NxHNxmJv2bQ • • http://www.drugabuse.gov/sites/default/files/images/colorbox/aslide28.gif Genetics and addiction •Susceptibility model – tries to explain why some substance users develop addiction while others do not •General heritability about 25% in mild drinking and 35% in heavy drinking (heritability estimates degree of variation of phenotypic trait in population) •Twin studies – strong genetic factor especially in males (almost no effect in females) and especially if alcoholism started before age 20 (little effect for later life) •In other drugs – the strongest influence of genetic factor in heroin (more than 50%), in other drugs similar to alcoholism (between 25-33%). •Huge discrepancy in studies, e.g. women are massively under-researched • • Genetics and addiction •Genes and environment determine addiction together •Inherited characteristic is a predisposition/risk factor, not a disease itself – addiction is a complex phenomenon with no single one determining factor •Research on genetics of addiction is not to push people back and feel miserable of unchangeable. It is for better treatment and prevention Genetics and addiction •Candidate gene studies – they try to find the concrete gene that is associated with the disease •Difficult to find such gene – many possible candidates and often contradicting results •Uncertainty about how much unique impact these genes have Reward-deficiency syndrome •Kenneth Blum •People with DRD2-A1 allele gene form (older variant) of D2 dopamine receptors are at higher risk of addictions. •30% of white population – they have up to 40% less dopamine D2 receptors •Feel less reward from normal activities – need stronger impulse •Feel more negative emotions and anxiety – take drugs to relief from negative states of mind • Reward-deficiency syndrome The Addictive Brain All Roads Lead to Dopamine.pdf - Adobe Acrobat Reader DC Evolution and addiction •Mismatch hypothesis •Addiction is a by-product of our brain structure •Reward system has significant evolutionary advantage, however, it brings susceptibility when high-dopamine sources become vastly available •High-dopamine society – humans have much stronger dopamine system than other primates. That probably evolved with increased consumption of meat and fish oil. Higher levels of dopamine in reward system increased our activity, motivation, orientation to goals, intelligence. People with lower dopamine functions (reward deficiency syndrome) have higher chance to misuse high dopamine sources Evolution and addiction •Mutualism hypothesis – plant-herbivore coevolution •Mammals have a long history of drugs-in-plants preference •Humans have preferences to ethanol (fermented in fallen fruits) •Humans have preferences to consume toxins in plants (e.g. nicotine, caffeine) as they were useful against parasites and bacteria Evolution and addiction •Life-history theory •Clear demographic pattern – males in their teenage and twenties are by far the most susceptible group •The same group is also at risk of risk-taking, violence, sensation-seeking,… - product of sexual selection – young male syndrome •Substance use and abuse is part of general risk-taking behaviours •Both risk taking and addictive behaviours decrease after mid 30s and after the person settles down •Higher risk taking is evolutionary effective in certain scenarios (e.g. during migration). Quantity vs quality investment strategy • •