Scientists Reveal The Link Between Genetics and Mental Illness

Scientists Reveal The Link Between Genetics and Mental Illness

Mental illnessHealth

What causes mental illness?

The causes of mental illnesses are a combination of genetic, biological, psychological, and environmental factors. Scientists have long since eliminated character defects or personal weakness as legitimate causes of mental illness.

Regarding the coping and recovery process, it is also not a matter of “sucking it up” or “pushing through,” despite what some uninformed individuals say; nor is coping and recovery a matter of self-discipline or willpower.

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While it is believed that our biology, environment, genetics, and psychology influence – to some extent – the onset of mental illness, genetics (heredity) seems to correlate the strongest. That is, developing a mental illness from parental genes is more likely than through biological, environmental, or psychological experiences.

Scientists Explain The Link Between Genetics and Mental Illness

mental illness

Heritable Mental Illnesses

“Most psychiatric disorders are highly heritable; the estimated heritability for bipolar disorder, schizophrenia, and autism (are) 80 % or higher … much higher than that of diseases like breast cancer and Parkinson’s disease.” – Burmeister, M., McInnis, M.G. & Zöllner, S.

Prior research has shown a relatively high heritability rate for the following mental illnesses:

  • Alcohol dependence
  • Anxiety disorders
  • Attention-deficit hyperactivity disorder (ADHD)
  • Autism and autism spectrum disorders
  • Bipolar disorder
  • Eating disorders (anorexia nervosa and bulimia nervosa)
  • Major depressive disorder (MDD)
  • Obsessive-compulsive disorder
  • Schizophrenia

Per a study published in Nature Reviews, the estimated heritability for bipolar disorder, schizophrenia and autism are between 75 to 90%, which is much higher than that of breast cancer (5-60%) and Parkinson’s disease (13-30%).

Mental Illness Symptoms and Rates of Heritability

Alcoholism

Alcohol dependence records a heritability rate of 50-60%, affecting around 5% of the population. The disorder is characterized by persistent problems involving tolerance, psychological cravings, and behaviors centered around alcohol use or its consequences. Alcohol dependence has an age of onset around the mid-twenties.

Anxiety and Panic Disorders are Among the Most Common Mental Illness

Anxiety disorders are quite common, with a prevalence rate of nearly 30%. Every diagnosed case of clinical anxiety involves a “heightened sense of arousal or fear.” Physical symptoms include rapid heartbeat and sweating; with psychological symptoms centering around worry and fear.

Panic disorder, defined as “debilitating anxiety and fear that arises frequently and without reasonable cause” has a heritability rate of around 50%.

anxiety

 

Childhood Mental Illness

Attention deficit-hyperactivity disorder (ADHD) symptoms include impaired attention capabilities and inappropriately-high levels of activity in quiet places, at work, or at school. Childhood ADHD is often marked by impulsivity, interruptive behavior, and constant fidgeting.

The prevalence of ADHD is around 8%, with an inheritability rate of 60-90%.

Autism and autism spectrum disorders (ASD) are a category of development delay disorders observed before age 2. Communication difficulties and engaging in repetitive behaviors are typical of autism and ASD patients. Symptoms of autism and ASD in toddlers include: not using gestures, withdrawal, loss of verbal or social skills, not using single words by 16 months or two-word phrases by 24 months, and not walking.

The heritability rate for autism and ASD is high – around 90%. The disorders are rare, with autism prevalence at .04% and ASD at .8%.

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Bipolar Disorder

Bipolar disorder, also referred to as manic-depressive disorder, involves periods of mania and severe depression. Manic symptoms include compulsive fluctuations in energy, mood, and rates of thought and speech. Depressive symptoms mirror those of MDD, which are described below.

The onset of bipolar disorder (BP) occurs during late teens or early adulthood. The heritability rate of BP is between 60-85% and affects approximately 1% of the population.

Eating disorders, consisting of anorexia nervosa (AN), and bulimia nervosa (BN), have an early average age of onset: in the early to mid-teens. Heritability rates are around .6% and 1%, respectively.

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