Addiction

Addiction is a compulsion to repeat a behavior regardless of its consequences. A person who is addicted is sometimes called an addict.

Physiological basis

Although the term addiction is sometimes often used loosely rather than as a medical classification, there are some physiological conditions related to everyday behaviors that are also related to the more commonly recognized mechanisms associated with addiction. Pleasurable activities cause the release of endorphins, and this endorphin-rush can conceivably become 'addictive'. Evolutionary biologists have suggested this process of attentuating pleasure pathways is part of the brain's natural system for ensuring that humans develop abiding interests. Since human societies depend on enduring attachments, many theorists suggest such addictions are not necessarily a problem. Other views, such as the those summarized in Buddhist concept of tanha, suggest trivial attachments are at the root of much human suffering.

Related Topics:
Endorphin - Tanha

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The pathways oriented to endorphins, sometimes called pleasure centers originated in small organisms such as insects, which rely on the neurological system to help them find familiar sources of food.

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Endorphins stimulate activity of the neurotransmitter dopamine after initially activating opioid receptors earlier in the nervous circuit. Increased dopamine activity is often met by a decrease in the number of receptors sensitive to dopamine. This process is called downregulation. The decreased number of receptors tends to result in reduced electrical activity along post-synaptic nerve pathways, unless some behavior or substance causes a continued high level of dopaminergic stimulation. The absence of a pleasurable sensation in conditions that were formally sufficient can cause a mild feeling of let-down after receptors have been downregulated. The increased requirement for dopamine to maintain the same electrical activity is the basis of both physiological tolerance and withdrawal associated with addiction.

Related Topics:
Neurotransmitter - Dopamine - Receptors - Downregulation - Receptor - Physiological tolerance - Withdrawal

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The middle striatal reward pathway has been most strongly linked with addictive and reward behavior. This pathway utilizes dopamine as a neurotransmitter and receives presynaptic input (from earlier in the circuit--it gets signals from these earlier in the circuit cells) from cells that respond to cannabinoids, nicotine (receptor subtype is nicotinic), and from cells that respond to endogenous opioid substances such as endorphins or enkephalins. Cells that are said to respond to a particular neurotransmitter (or agonists) contain, at the postsynaptic end (receiving area of the cell) receptors for that neurotransmitter. Many believe that there are more neurotransmitters involved with addiction than just dopamine including serotonin, norepinephrine, and the endocannabinoid anandamide.

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In cases of physical dependency on depressants of the central nervous system such as opioids, barbiturates, or alcohol, the absence of the substance can lead to symptoms of severe physical discomfort. Withdrawal from alcohol or sedatives such as barbiturates or benzodiazepines (valium-family) can result in seizures and even death. By contrast, withdrawal from opioids, which can be extremely uncomfortable, is rarely if ever life-threatening. In cases of dependence and withdrawal, the body has become so dependent on high concentrations of the particular chemical that it has stopped producing its own natural versions (endogenous ligands) and instead produces opposing chemicals. When the addictive substance is withdrawn, the effects of the opposing chemicals can become overwhelming. For example, chronic use of sedatives (alcohol, barbiturates, or benzodiazepines) results in higher chronic levels of stimulating neurotransmitters such as glutamate. Very high levels of glutamate kill nerve cells (called excitatory neurotoxicity).

Related Topics:
Depressant - Central nervous system - Barbiturate - Neurotransmitter

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Opioids present extreme risks of dependency because they are chemically similar to endorphins, causing an upregulation of dopaminergic receptors without stimulation of the endorphin systems. Cocaine and amphetamines also pose risks associated with physical attenuation, in both cases because they cause increases in the levels of the neurotransmitters dopamine and norepinephrine which acts indirectly to stimulate dopaminergic pathways in the brain.

Related Topics:
Opioid - Cocaine - Amphetamines - Norepinephrine - Brain

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