Is Drug Addiction Genetic?
Genetics vs. Heredity: What’s the Difference?
The terms genetics and heredity are sometimes used interchangeably, but there are differences that are important to understand.
- Genetics refers to the study of genes or heredity.1,2 Genes are units of DNA that are passed down from parents and specify certain traits.1 Genes are housed on chromosomes. Humans have about 20,000 genes arranged on their chromosomes.3 People have 46 chromosomes in 23 pairs. Individuals inherit one of each pair from their mother and one of each pair from their father.4 This happens at random, which explains the differences between siblings. Individuals share about 50% of their genes with first-degree relatives, like parents, siblings, and children.5
- Heredity refers to the way that different characteristics and traits are passed down to from parents to children through changes in genes and the DNA sequence.6 An inherited trait is genetically determined.7 Not all traits are strictly genetic. In addition, the expression of many genes is also influenced by the environment.7 However, heredity accounts for certain traits, such as height and eye color.1
Since parents pass on certain genes to their children, certain diseases that are linked to genetics might be said to “run” in the family.6 Changes in DNA and genes can affect the risk for certain diseases, but it’s a complex story, and DNA can even be “remodeled” by exposure to different environmental factors.1 Some diseases, like cystic fibrosis, occur due to mutations in a single gene.1 However, many conditions, including addiction and other health complications, are thought to develop as a result of several potential genetic and environmental factors, as well as the interplay between these various influences.1
What this means is that even if you have a family history of addiction, you’re not necessarily guaranteed to develop an addiction. You need to have access to the drug, use it repeatedly, and be exposed to certain environmental influences in order to develop an addiction. In general, genes are thought to account for about half of a person’s risk of addiction.1
Environmental and Other Contributing Factors
Many factors play a role in addiction. Complex interactions between an individual’s genes and the environment, including their upbringing—as well as other biological, social, and cognitive factors—can potentially increase someone’s overall risk of substance use and addiction.8 Some of these factors can include: 9-14
- Exposure to adverse early life experiences. Trauma, abuse, neglect, or witnessing domestic violence can have a negative effect on brain development and certain brain structures, which can impact behaviors related to addiction, such as impulse control, decision-making abilities, emotional regulation, and social and emotional skills.
- Other family factors that influenced childhood experiences. This may include factors such as parental substance use, poor role modeling, poor parental supervision, a lack of emotional warmth, or parental rejection.
- Environmental factors. Living in an area with high crime rates, having low socioeconomic status, having easy access to substances, starting to use substances at an early age, seeing community norms regarding substance abuse, or being unemployed can increase an individual’s risk of substance use and addiction. In addition, chronic exposure to negative environmental factors may be associated with certain brain changes that can lead to altered behaviors, such as impulsivity and sensation-seeking, that could further increase the risk of addiction.
- Learned behaviors combined with brain changes. This can occur, in part, due to the reinforcing effects of the substance, which means that the pleasurable effects of using the substance can cause someone to want to use it again. Repeated substance use can cause brain changes that impact the brain’s reward circuit, which can also result in feelings of extreme stress when the substance isn’t taken. These changes, combined with exposure to certain Pavlovian conditioned drug-related cues, can impact addiction. Pavlovian conditioned cues include factors—seeing pictures of alcohol, for instance—that occur in combination with pleasurable experiences, such as being with friends or being in a pleasant environment. This can trigger certain behaviors and responses that reinforce the desire to use the substance.
Inflammation / neuroinflammation. There is some research evidence suggesting that various inflammatory processes may play a role in the development and course of substance use disorders and other mental health issues (which may one day offer novel treatment targets).21
- Psychiatric factors, some of which may have a genetic component. This can include having mental health issues such as schizophrenia, major depression, and personality disorders, which are often associated with addiction.
Are There Addiction Genes?
There isn’t just one addiction or alcoholism gene.15 Scientists have identified multiple genes associated with addiction, in general, as well as genes associated with addiction to specific substances.16,17 Although research in this area is ongoing, some of the genes associated with addiction—and protection against addition, too—include:1,16-18
- Alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2; mitochondrial aldehyde dehydrogenase). These genes play a role in the metabolism of alcohol. Genetic differences that lead to higher ADH1B activity or lower ALDH2 activity can result in an individual experiencing uncomfortable symptoms if they drink alcohol; such variations in gene expression may have a protective effect against alcoholism.
- GABRA2 and CHRM2. These genes have been linked to alcohol use disorder (AUD)—a medical condition defined by the uncontrollable use of alcohol despite negative consequences. In addition, both of these genes appear to be strongly associated with early onset alcoholism.
- MAOA, SLC6A4, COMT, and other genes associated with stress resilience. People who have these genes may have individual differences that impact stress responses, which, when combined with other influences, could impact addiction.
- CHRNA2. Researchers have found that low levels of expression of this gene are associated with cannabis use disorder (marijuana addiction).
- CUL3, PDE4B, and PTGER3. A large study of an international database found more than 400 locations in the human genome and at least 566 variants in these locations that are related to smoking or alcohol use. CUL3, PDE4B, and PTGER3 were specifically identified as playing a significant role.
- HIST1H2BD. This was identified in one study as being associated with cocaine dependence.
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How Are Genes Tested?
Specific genetic testing may one day help better identify individual susceptibility for addiction. Health care providers see the benefit of genetic testing to potentially help determine a person’s unique addiction risks, but it’s an area that requires more research.1
Lots of scientists have collected lots of data in this area, but different software system and measurement formats make it difficult for them to share data. The National Institutes of Health (NIH) created the Big Data to Knowledge (BD2K) program to help scientists use big data and data science in their research in an effort to glean more genetic information that might give disease insights.1
There’s often disparity in how individuals respond to treatment. Part of that is because of genetics. Genes effect the numbers and types of receptors in the brain. Genes that code for cytochrome enzymes in the liver (CYP variants) can influence how quickly an individual metabolizes a drug, which influences how they respond to medications and other substances. Pharmacogenetics is the emerging science that will help health care providers improve treatment by tailoring medications to an individual’s genetic makeup.1
Overcoming Addiction and Finding Treatment
Even if you have a genetic predisposition to addiction, you can take steps to manage your risk and minimize your chances of addiction. If you or someone you care about are struggling with addiction, you should know that treatment can help you start the path to recovery to overcome addiction.
Treatment can help you understand addiction and your triggers, teach you ways to prevent relapse, and help you develop better stress management and coping skills so you can abstain from using drugs and alcohol. Treatment should be individualized to your unique needs, which can include your physical and psychological health, as well as social, vocational, legal, and other needs.19
The first step in recovery might be to enter detox so you can receive support while withdrawing from the substance. Detox can keep you safe and comfortable as your body detoxifies from the substance.19 You might then enter an inpatient rehab, where you live for the duration of treatment and receive round-the-clock care and support, or outpatient rehab, where you live at home and travel to a facility for treatment. Inpatient and outpatient rehab can occur on a variety of levels of intensity and can last for different lengths of time that can depend on your unique needs.20
Interventions and/or addiction therapies you may receive during treatment may include: 19,20
- Medication. Depending on the substance you use, you may receive medication to help you through the withdrawal period, as well as medication to help you avoid drug or alcohol use and help prevent relapse once you’re in recovery. The treatment center may use pharmacogenetic testing to help find the best medications for you and to reduce the risk of adverse effects.
- Behavioral therapies. This can include a wide range of therapies such as cognitive-behavioral therapy (CBT), designed to help change thoughts and behaviors related to substance use; or motivational interviewing (MI), which can help people resolve any ambivalence toward their recovery needs and better engage with treatment efforts. Behavioral therapies are often provided in both individual and group therapy settings.
- Mutual support groups, such as Alcoholics Anonymous (AA) or Narcotics Anonymous (NA). You may benefit from ongoing support from others who are also in recovery.