Comorbid Disorders: Drug Addiction and Mental Illness

 

Despite research confirming addiction as a chronic, often relapsing brain disease, people still argue that since the initial decision to take drugs is voluntary, addiction is simply a series of bad decisions by the morally weak. Drug addiction is a disease because the abuse of drugs leads to changes in the structure and function of the brain.

People need to understand that at least half the people who seek help with addiction or mental-health treatment have co-occurring disorders. These are known as "comorbid" disorders. When two disorders or illnesses occur in the same person, simultaneously or sequentially, they are described as comorbid. Comorbidity also implies interactions between the illnesses that affect the course and prognosis of both. 
 
Research (2007) reveals that this type of dual diagnosis may stem from a common cause: developmental changes in the amygdala, a walnut-shaped part of the brain linked to fear, anxiety and other emotions.

Andrew Chambers, MD, reports epidemiological data says that from two to five of every 10 anxious or depressed people, and from four to eight of every 10 people with schizophrenia, bipolar disorder, or antisocial personality, also have some type of addiction.

This complex, seemingly intractable pairing has been attributed in the past to "self-medication.” Yet, newer research is providing models for understanding a shared neurobiological basis for and complex interactions among psychiatric symptoms, drug exposure history, and addiction vulnerability.

By far the most common issue connecting mental illness and substance abuse is the intention of patients to medicate the mental health symptoms that they find disruptive or uncomfortable by using alcohol and drugs.

Some examples include:

• The depressed patient who uses marijuana to numb the pain
• The patient suffering from social anxiety who drinks to feel more comfortable in social situations
• The patient who struggles with panic attacks and takes benzodiazepines like Xanax or Valium in order to calm the symptoms or stop the attacks before they start
• The patient with low energy and lack of motivation who takes Adderall, cocaine or crystal meth to increase their drive to get things done
  (The National Bureau of Economic Research)
  

Chambers would like to see educators, counselors, physicians, and scientific researchers integrate insights into both mental health and addiction given that "dual-diagnosis cases are the mainstream among these patients, probably because addiction and mental illness are strongly linked by neurobiology."

 

What may harm the amygdala early in human development? Dr. Chambers cites the following:

1. Relatively rare cases of temporal lobe epilepsy,
   
2. Tumors or early brain injury,
   
3. Far more common, complex interactions among subtle genetic and environmental factors that change the way the amygdala functions or is connected to the rest of the brain during childhood and adolescence. 
    
   For example, Chambers says, "Early emotional trauma, paired with a certain genetic background, may alter the early development of neural networks intrinsic to the amygdala, resulting in a cascade of brain effects and functional changes that present in adulthood as a dual-diagnosis disorder."
   

( R. Andrew Chambers, MD, Tammy J. Sajdyk, PhD, Susan K. Conroy, BS Joan E. Lafuze, PhD, Stephanie D. Fitz, BS, and Anantha Shekhar, MD, PhD. "Neonatal Amygdala Lesions: Co-Occurring Impact on Social/Fear-Related Behavior and Cocaine Sensitization in Adult Rats.” Indiana University School of Medicine; Behavioral Neuroscience, Vol 121, No. 6. December 2007.)

James Garbutt, MD, professor of psychiatry at the University of North Carolina at Chapel Hill and research scientist at UNC's Bowles Center for Alcohol Studies, puts co-morbidity like this:

“Mental illness and alcoholism or drug abuse interact in a complex dance. Mental illnesses can increase the risk for alcoholism or drug abuse, sometimes because of self-medicating. On the other hand, alcoholism can lead to significant anxiety and depression that may appear indistinguishable from a mental illness. Finally, one disorder can be worse than the other."

Linda Foster -- developmental psychologist and member of the Author’s Guild, American Medical Writers Association, the American Mathematical Society, and Media Bistro – cites other factors that could explain the frequent simultaneous occurrence of addiction and mental illness, including:

• Genetics. Genetic factors seem to account for some of the co-morbidity (having both disorders at the same time) of substance abuse and mental disorders. Studies comparing identical and fraternal twins found more instances of having two disorders among the identical twins, indicating that genetics likely play some role.
• Chemical deficiency. Neuro-chemical factors were also found to be a common thread when mental disorders and addiction occur together. A reduction in the amount of serotonin, a chemical critical to brain functioning, may be the reason that alcoholism and anxiety disorders coincide so often. There is also evidence that addiction and mental disorders are associated with the dysfunction of a group of brain chemicals called monoamine oxidases.
• Shared environment. Studies surrounding twins also showed that environment plays a major role in having both a substance abuse problem and another mental disorder.
  
  
  (Linda Foster MA. “How Mental Illness and Addiction Influence Each Other. everydayhealth.com. April, 20, 2009.)
  
  The Hazelden Betty Ford Foundation even describes a “supersensitive model” concerning why these disorders occur together:
  
  
  People with mental illnesses may be more susceptible to the harmful effects of alcohol and drugs. For example, it appears that at least 50% of the general population can drink alcohol without developing problems, but only 5% of schizophrenics can drink without developing problems. And people with schizophrenia appear to have a much harder time recovering from alcohol/drug problems: they have more relapses and spend more time in the hospital than non-schizophrenics, even though their severity level is the same.”

Mental illness – addiction: both of these afflictions are treatable, yet both carry stigmas that prevent many people from understanding the complexities that comprise their true identities. When the two are comorbid disorders, their shared neurobiological basis blurs which is which.

My question is: “Should it really matter to the public whether mental illness or addiction causes the suffering?” We must treat all of those with brain diseases – mental illness, addiction, co-morbidity – so that they can have a healthy, productive life. Much more research needs to be done to further the study of the connections.

Consider the link between post traumatic stress disorder and substance abuse. The prevalence of substance abuse disorders in individuals with posttraumatic stress disorder (PTSD) is high. Mill et al. reported that individuals with opioid dependence had the highest prevalence of PTSD (33%) compared with all other substance use. 

(K.L. Mills, et al. “The impact of post-traumatic stress disorder on treatment outcomes for heroin dependence. Addiction. 2007.)

Members of the military returning from combat operations often exhibit a co-occurring triad of posttraumatic stress disorder (PTSD), traumatic brain injury (TBI), and pain, which complicates the problems with substance abuse.

"We do not know enough yet to predict precisely whether one disorder will lead to the other(s) or how to prevent comorbidity," said NIDA Director Nora D. Volkow, M.D. "We do know, however, that the high rate of comorbidity means that we need a comprehensive approach to intervention that identifies, evaluates, and treats each disorder concurrently." It is often difficult to disentangle the overlapping symptoms of drug addiction and other mental illnesses, making diagnosis and treatment complex. 
 
Please click here to access an informative, comprehensive report on comorbidity from the National Institute on Drug Abuse: https://www.drugabuse.gov/sites/default/files/rrcomorbidity.pdf