Robert Downey Jr.’s Son Drug Arrest and the possible Genetic Link to Addiction

photo of a young man in handcuffs after being arrested

The Role of Genetics and Increased Susceptibility to Addiction

In 2013, Indio Downey, the son of actor Robert Downey, Jr. was charged with felony cocaine possession. Shortly after his son’s arrest, Downey released a statement to a celebrity news website, TMZ: “Unfortunately there’s a genetic component to addiction and Indio has likely inherited it.”[1] Scientists are actively researching the role that genes play in the disease of addiction, as well as how addiction may be inherited.

The Possible Link to Inherited Genes and Addiction

DNA Double HelixEvery living thing, from plants to animals and people, are made up of cells. In the nucleus or command center of each cell, these are strands of DNA (deoxyribonucleic acid). These long, ladder-shaped molecules are packaged into chromosomes. Humans have 23 pairs of chromosomes, while fruit flies only have four. Chromosomes are made up of continuous strands of genes. Genes provide the code, or recipe, for the body to create proteins. Proteins are important because they carry out most of the body’s functions.[2] If certain genes are present, go missing or have mutated, the proteins that they code for will be altered.

Susceptibility to Drug AddictionStudies have shown that addiction, the predisposition to substance dependency and the vulnerability to relapse after treatment are genetically related.[3] The American Psychological Association reported that “at least half of a person’s susceptibility to drug addiction can be linked to genetic factors.”[4] Like other medical diseases, addiction involves complex genetic variations. When combined with environmental factors, the genetic inclination towards addiction is inherently difficult for some people to overcome.

In their search for the biological differences that make people more susceptible to addiction, scientists have identified some genes that may play a role. These include the opioid receptor mu subunit 1 (OPRM1), 5-hydroxytryptamine receptor 1B (HTR1B), Period1 (Per1), Period2 (Per2) and the Neuropeptide Y (NPY) genes.



OPRM1 encodes for the mu opioid receptor (MOR) protein. MOR, in turn, plays an important role in substance dependence because it controls the dopamine system.[5] In studies, patients with the OPRM1 gene have shown “clinically observable changes in stress responsivity, vulnerability to opiate addiction and alcoholism.”[6]


HTR1BThe HTR1B gene encodes for the 5-hydroxytryptamine receptor 1B protein, also known as the 5-HT1B receptor. The highest concentrations of 5-HT1B receptors are found in the central nervous system where it controls the creation and release of serotonin, a chemical that is associated with feelings of contentedness and well-being.[7] A study in Pharmacology, Biochemistry, and Behavior found that mice without the HTP1B gene have demonstrated an increase in aggression.[8] The American Journal of Medical Genetics reported that those lacking the HTP1B gene also have a higher predisposition for alcohol, cocaine and heroin abuse.[9]








Per1 and Per2

Per1 and Per2
Per1 and Per2 genes aid in regulating circadian rhythms. The National Institute of General Medical Sciences defines circadian rhythms as, “physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment.”[10] Mutations in the Per1 and Per2 genes result in the disturbance of these cycles. These disruptions have been found to increase alcohol intake,[11]which in turn contributes to alcohol abuse and relapse.[12]

Neuropeptide Y

Neuropeptide YAnother gene that influences alcohol consumption is Neuropeptide Y (NPY). Like the Per1 and Per2 genes, NPY influences a person’s circadian cycles, as well as stress response. Studies show that if NPY undergoes polymorphism (changes to a different shape) then the resulting gene signals for a protein associated with greater alcohol intake.[13]

How are Genes Passed Down?

Heredity is the transmission of genetic information from one generation to the next. Each human being inherits or acquires twenty-three chromosomes from his/her mother and the same number from his/her father to make a total of twenty-three chromosome pairs. This is how traits are passed from parent to offspring. If one or both parents have a gene that predisposes them to addiction, the chances are their children will also have the same gene.

Inheriting Addictions

One year after the arrest of his son, Robert Downey Jr. told Vanity Fair that Indio “probably inherited his addictions.” When Downey was six, his father, Robert Downey Sr. allegedly started supplying him with marijuana. This was the beginning of Downey’s long history of substance use, which includes his arrests for possession of heroin, cocaine, and Valium, as well as time, served in prison for missing court-ordered drug testing. [14]

When Downey was six, his father, Robert Downey Sr. allegedly started supplying him with marijuana.The Collaborative Study on the Genetics of Alcoholism assessed the genetic transmission of habitual smoking as well as alcohol, marijuana and cocaine dependence in families. The results confirm that the vulnerability toward addiction is an inherited trait. Researchers found that children of addicts were eight times more likely to develop an addiction themselves.[15]

Chance to Develop AddictionIt is vital to note that susceptibility to addiction does not guarantee that the disease will be contracted. In Clinical Pharmacology & Therapeutics, scientists reported that “addictions are a diverse set of common, complex diseases that are to some extent tied together by shared genetic and environmental etiological factors.”[16]

Behavioral neuroscientist Karen Ersche of the University of Cambridge in the United Kingdom and her associates conducted research to determine if inherited genetics was the sole cause of substance abuse. Fifty pairs of biological siblings, one with an addiction and one without, were evaluated for poor self-control, a symptom synonymous with the brain circuitry of addiction. Not surprisingly, both sets of siblings were found to have the same low amount of self-control. Researchers concluded that although some individuals are biologically predisposed to addiction, the disease is not inevitable and can be overcome.[17]

The Significance of Genes in Addiction Treatment

When a gene is discovered to influence substance abuse and addiction, scientists are then able to turn their attention to developing a drug that modifies that gene’s activity. Dr. Joni Rutter, director of the Division of Basic Neuroscience and Behavioral Research at the National Institute on Drug Abuse (NIDA), explained that these “studies, by pinpointing which genes drugs activate or silence, can shed light on the specific proteins and processes involved in addiction. And, if we can then prevent or reverse those effects, we may have powerful tools for preventing and treating addiction.”[18]

Overcoming the Disease of Addiction at Seaside Palm Beach

Seaside’s treatment programs address the patient’s emotional, physical and mental health.Our mission at Seaside Palm Beach is to provide our patients suffering from substance abuse disorders with the finest care in elegant and peaceful surroundings. With customized therapies that incorporate the latest, clinically-proven techniques, Seaside’s treatment programs address the entire patient’s emotional, physical and mental health.

From medically-assisted detox to post-treatment support, Seaside enables patients to overcome their addictions by helping them to integrate wellness into their everyday lives. When you or a loved one is ready to start the journey to overcoming the disease of addiction, please contact a specially-trained counselor at Seaside Palm Beach.


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