Mental Illness: Genetic or Environmental?

MondayThe currently held belief is that the answer to this question is both. This theory is called the Two-Hit hypothesis of pyschiatric disorders. First, one must be genetically pre-disposed to developing a mental illness, but there must also be an environmental impact that triggers the development of the illness.

It is commonly thought that there are four key elements involving the development of pyschiatric disorders:

1) genetic vulnerability
2) life event stressors (divorce, abuse, etc.)
3) the individual’s own personality, coping skills, and support network
4) external event triggers (illness, toxins, etc.)

Without the predisposition to mental illness, you won’t develop schizophrenia, bipolar or even major (chronic) depression. Conversely, you could be genetically predisposed and never develop the illness. In a study of mental illness in twins, they found that for identical twins, there was a 50% chance that both twins would develop schizophrenia, while there was 15% chance for fraternal twins. With bipolar disorder, there is up to an 80% chance that identical twins will both develop the illness, while the rate is only 8-10% for fraternal twins.

What is also interesting is that it is believed that your personality, coping skills, and support network may act as a “filter” between genetics and the triggering life event. This may help reduce the impact of such an event. Likewise, an individual lacking any of the above may actually perceive the life event as more stressful and the personality filter may become more of a magnifying glass.

All genetic susceptibilities may not be created equal. For example, schizophrenia is thought to require only minor stressors in order to manifest the illness while depression may require moderate stressors. Major or overwhelming stressors can produce post-traumatic stress disorder (PTSD) in anyone, regardless of genetic predisposition.

Mental illness is a complex paradigm with both genetics and experiences playing a role. This information makes me feel better personally because I no longer feel like my bipolar is a personality flaw. I can identify in hindsight some life events that could have triggered my illness- my parents divorce for example. But knowing that genetics are only a part of the equation helps too – it reaffirms that if I had chosen to have children they would not be destined to become bipolar.

All data and scientific information is from the text: Essential Psychopharmacology: Neuroscientific Basis and Practical Applications, Second Edition by Stephen Stahl. Any errors in transcription or translation are entirely mine. I am not affiliated with the medical field in any way.

© Monday and A Canvas Of The Minds 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Monday and A Canvas Of The Minds with appropriate and specific direction to the original content.


41 thoughts on “Mental Illness: Genetic or Environmental?

  1. Great post, full of meaningful information! I’m a poster child for a person with a heavy genetic predisposition, a sensitive constitution, and traumatic life event overload. Voila. Unfortunately, my son did inherit The Beast. On the positive side, though, he’s got the creative fire, brilliant intelligence, and energy to carry it through. And he’s taking good care of himself, having lived through being my child. I’m rooting for him, that he should learn how to use the fire for creative good works, and learn how to keep it under control, so that neither he nor his loved ones gets scorched.

  2. This post is absolutely fascinating to me, and I’ll tell you why. Genetic pre-disposition. By all accounts and purposes (at least according to how modern medicine looks at things), I have absolutely none. There is zero history in my family of anything, going back generations. And we have examined the subject very closely. I don’t even have a Great Aunt who had to “go away,” nor an uncle that nobody talks about, or who was even considered “quirky.” I did have one uncle who had addiction problems, but the consensus seems to be that they were entirely that. They didn’t manifest because of mental illness or life trauma.

    So that means whatever is genetic in me is was hidden, or that they haven’t yet hit upon it. I read some interesting theories about manic-depression potentially being the result of a yeast, or even the virus that causes mononucleosis. Both of these could make sense in the context of my life, but a great deal more research is needed.

    Even as far as life stressors – well I won’t deny that moving from Pittsburgh to Here when I was nine had a big impact on me. And maybe that was enough. But I have always possessed pretty decent coping skills, and the environment I was raised in was above and beyond, as far as being healthy and supportive.

    Let me just stress that I am in no way contradicting the information you have presented. It’s accepted as the standard in the field, and everyone I know with any form of mental illness can point to those factors. It just makes me wonder more about how I ended up this way! 😉

    • It is something that can lay dormant in generations of people, from what I understand. At first, I thought it came from my dad’s side. Everyone was kind of off and usually had some wild behaviors.

      I found some kind of ancestry thing for my maternal grandfather’s family. It seems that somewhere in the 19th century, one of my ancestors was institutionalized for his entire life, a short life of 52. He died there. Reason isn’t clear. Some records say idiocy and some say lunacy.

      I’m guessing it likely has something to do with BP. So, you never really know what’s floating around your gene pool!

      • This is true, except my mother has literally traced my family back centuries, to when they lived in Ireland. I don’t think she has gotten quite as far with my dad’s side, but she’s close. We have birth and death and war and census records, and we have come up with absolutely nada, which has been pretty astonishing to most of the doctors I have spoken with. Not impossible, but definitely very improbable!

        • Luna is right about the possibility of it being something that lays dormant in generations of people–if BP is indeed genetic or has any semblance of being a genetic predisposition to begin with.

          You can take my bone condition as a prime example of a carried dormant gene mutation. My bone condition has been carried from one of my parents, none of who turned up with the “disease” or rather it lies in one of them, but for them the trait is recessive/dormant (and I don’t know which one because my dad refused to do a genetic test when I was admitted to hospital and they were offered a free chance). And we know of no one in the family with brittle bones. It just turned up dominant in me.

          BP can be like that. At least, it’s a possibility, but much more complex I assume. I wish I knew about my ancestry as much as you do Ruby. All I know is I’m Colombian and I must have what Colombians generally have genealogically–Spaniard ancestors of course, then there’s Incas and, in my case, the Quimbaya and Chibcha natives of my region, oh and I’m sure the Turks and Persians from pre-Colombian Spain and apparently a lot of Germans migrated to Colombia during WWII which could explain the fair-skinned and blue-eyed relatives in contrast with the browner relatives, but I know NOTHING, nothing significant to MY family. Well, there’s the the rumor that my great grandma on my mother’s side slept around a lot (which was a major “sin” and she was shunned), and that as a result my great-grandfather was black (another shock since Colombians were pretty bad at segregating each other from the African descendants in that region).

          All I know is that my aunt committed suicide (from what I hear she very much fits the BP type), my mom apparently also attempted suicide post-partum; her uncle died in an asylum, there was lots of abuse in her family and another uncle of mine (her youngest brother) was shot. It was rumored that he was prostituting himself for drugs. Then my brother is OCD and we both got some PTSD. That’s enough to convince me of many things.

    • Has there ever been any depression in your family, Ruby? My psychiatrist told me that bipolar tends to run in families with depression. Also, it could have been any kind of environmental trigger – a virus or something else – that caused the illness to manifest. It doesn’t have to be an emotional trigger.

      • No depression, Monday. My family is astonishingly healthy, both mentally and physically. But I agree about the environmental trigger. As I mentioned, I have read about manic-depression perhaps being related to a yeast, or Epstein-Barr virus, which causes mononucleosis (among other things).

        Yeast I am highly susceptible to. Of course there is the reaction to antibiotics that many women know too well, but I also had thrush – a yeast infection in the throat, common in babies and young children but not so much as you age – as an adult. And I had mono at least two, more likely three or more times in my life. This is also not a common occurrence, though not the impossibility doctors once believed.

        Again, these theories are only that, theories, in the very beginning stages. But they sure as heck would explain a great deal about me if they were substantiated!

        • Yeah, the further the generations, the less probable. That is why if they were ever to isolate one gene that is responsible, only half of us would probably end up with the anomaly. Then there’s the question of the other half, right?

          And, in your case, it may have been partial deletion as a result of inheriting just the perfect combination of genes between your parents to create it. Or, it could have been some environmental toxin that created partial deletion(s). Something like that.

          Once they have all of this mapped, I’m sure our subtypes can be better classified by the partial deletions and what function they are responsible for. But, for now, all we can do is offer our gene samples, follow the research, and support researchers the best we can.

          • From what I have been reading, there isn’t one gene that is responsible, but rather a combination of genes that must be present and then activated. (I don’t think they know which ones either.) A partial deletion is a very possible explanation – perhaps your mother caught a virus while she was pregnant – who knows? The human body is such a mysterious thing in so many ways. I don’t know if they will ever solve the problem. Heck, in 20 years they may have a completely different theory!

            • I don’t think that it’s coincidence that my brother has moderate classical Autism, I have Bipolar Disorder, and my son has PDD-NOS on the Autism Spectrum. That’s why I think there are all kinds of things responsible for symptoms that simulate developmental disorder and mental health disorder. It seems in my family, certain conditions on the Y and X chromosomes are present and responsible for changing brain chemisty.

              In other families, genetics may be less evident. So, it could be entirely environmental. There are all kinds of chemical agents present in our environment today that could possibly be genetically altering. Things that we probably won’t know about in our lifetimes.

              For me, it can’t be environmental. My father and mother grew up in two totally different parts of the US. My husband and I were born in different parts of the country. My brother and I were borm in different parts of the country. The only link is that my mother, my brother, and my son were all born in Pittsburgh. Apart from that, there is no constant.

              My father is not diagnosed, but we are one in the same. The only oddity is that my brother and my son are not the same. My brother has an obvious pervasiveness and obsession. My son does not. My son has a speech delay. But, at three, he already has speech that rivals his. However, it is clear to me that my son is not the same as other kids.

              So, by this logic, I can probably predict that I will have a daughter with BP. Only if that requires only one affected X gene. My husband shows no signs of BP. The only other BP diagnosed is my biological third cousin(s?). (Maybe two). My sister, biologically my third cousin, is diagnosed BP I. That begs the question. Does my mother have an inactive BP gene? Why do I have BP II and she has BP I?

              Like I said, in my case, clearly genetic. And it makes me wonder how ASD and BP are connected. That cannot be coincidence.

  3. Hi 🙂

    Loved the post and am so excited/encouraged by the blog.

    Keep up all the good work.

    Kind Regards,


    • Thank you for your response, Kevin! I love Manic Monday’s posts because they are so very different from my own, and always quite educational. We appreciate your encouragement so much. 😀

  4. I remember seeing this in many a book and class during my run at my Psychology B.S. Scientists are working hard to identify the gene(s) that might be responsible for various mental illnesses. They figure it’s likely that there is a possible partial deletion that disruptions typical brain functioning. Essentially, it means that we are wired differently from birth.

    I started to read a book about the prevalence and onset of bipolar disorder and schizophrenia among twins. Your information is absolutely correct. So, we know why there is an urgency to find these genetic deletions or partial deletions that may be responsible. It may be one. It may be many. (It’s likely a few). After that, it’s a matter of working on gene therapy to possibly replace what is missing.

    So, this begs the question. If you have the option of gene therapy to remove your disorder, would you?

    • Gene therapy to “correct” my bipolar disease? Hmmm, let’s see….probably would have had a better chance of surviving my childhood, which was filled with verbal and emotional abuse, so I might not have such severe PTSD from that. Probaby would not have been in the situation that set me up for being drugged and raped as a 16 year old, so ditto with the PTSD from that. Then I very likely would not have run away and lived on the street, doing things that young girls who live on the street do in order to survive. Need I go on? I’d take the cure, especially if it could have been given to me as a child.

      • I don’t know if gene therapy could have prevented the PTSD. And I think about any kind of PTSD I have (and I think I do have it. I’ll share in an upcoming post), and I wonder if the bipolar disorder made it worse, it stopped it from becoming any worse.

        I could see the running away thing. But, it sounded like you needed to get out of that environment. Not having bipolar disorder would have made you stay. Would it have made the PTSD any worse?

        And what of the good things bipolar disorder has done for you. I know there’s plenty of bad to reflect on, but what of the good? Did it play a part in getting through PTSD and becoming a doctor? Or even just the heaviness of med school?

        I love questions that involve the changing of the time-space continuum. It makes you think of the “what-ifs” without dwelling on them!

        • Sorry, I wasn’t writing clearly. Must have been the brain fog from last night’s bad night.

          What I was trying to express re: my PTSD is that it is a result of 1) being a neurologicaly atypical child of an abusive mother, which BP did NOT help with, probably the opposite. 2) My BP had everything to do with being an abandoned child on the streets, being essentially a child prostitute, surviving on things like after-dinner mints for days at a time. 3)I guess my native intelligence and creativity could have some connection to being neuro atypical, but whatever good it’s done me, it’s done me ten times worse. No, I would not choose it again, I do not love it, and I would not recommend it to a friend. And, by the way, raising a BP child and watching his suffering, suffering with him, fighting for his life, reaffirmed time and time again that I would not wish this on anyone. I would go for the gene therapy, pronto! My medical career, you ask? Destroyed beyond repair. Sleepless nights and mania don’t mix. Been there, done that, and that door is closed. So, no, I do not find any positives, personally, in my own life, in my own mind.

          • You raise excellent points, Laura, and I wish for all of the good things you’ve done for others to come back to you ten-fold. You are the most deserving after the trials you have endured.

            The most underscored point was raising a child with BP. I worry about my son. With all of the disorder floating around my family, I have no idea what is lying dormant in there. It’s clear that he has developmental delays, and a therapist has declared atypical autism. I’m not sure, because it doesn’t fit. We’ve been there. As I watch him grow, I see volitile reactions (from me) abd anxiety (OCD and PD from C.S) He is moody, sensitive, and terrified of crowds of people he doesn’t know. Anytime he gets dirty, he insists on a bath.

            Maybe I’m reading too much into it. But, that is one of the serious disservices bipolar disorder has done for me, if I could name the worst. Besides being a bipolar mother.

          • Oh, and I forgot. If I could get my son the therapy, he’d get it. He doesn’t need it. If I could help it, I would take all of that away.

    • Lulu, you are correct that there is not just one gene responsible for mental illness. There is also a section in this text that discusses gene migration issues resulting in epilepsy, mental retardation, autism and possibly schizophrenia. Any number of sources can cause the brain to be wired differently either while in development or at latter points. I think any gene therapy that could be done, would have to be done during neurodevelopment. If I could do it now, just erase the illness today? Well, I’ll have to think on that and write a post. 😉

  5. “I no longer feel like my bipolar is a personality flaw. I can identify in hindsight some life events that could have triggered my illness”


    I struggled – still do some days – with this particular issue.

    On the topic of genetic disposition, I don’t know of anyone in my family that has had bipolar, but a close family member does have bouts of depression. Of course, it could just be the case that in the past the members in my family with the genetic disposition for bipolar didn’t have life events etc that triggered the illness.

    • Pompeii, in regards to the quote, I also struggle with it, even now. I have obsessed and read so much about this nature vs. nurture paradigm over the last eight years or so, even prior to my own diagnosis. There’s just so much varied research out there, and then there’s the memes you’re brought up with– the cultural too. I was brought up believing that mental illness as non-existent, an infirmity, a transient thing (and this last one has a grain of truth). And even though I was brought up in the U.S., I was raised with a Latin American cultural view of mental illness plus the religion my parents got into when I was in my early teens. I was just left questioning myself and everything else about the matter.

      Yet, I know that both genetic disposition and environmental factors are at play. In my case, I feel it’s more environmental. I’ve had pretty traumatic experiences throughout my life (and they seem to keep coming). Add to that the fact that my mom comes from a line of suicides and “crazies” and that she was physically abusive towards me.

      Saying the human mind is so complex is an understatement; we really do host a universe inside. I guess I’m still left wondering…

      • P.A.Z., I really hope you wonder more than struggle, if that makes sense. I know that different cultures and different religions hold very different views on mental illness, but as I said in my comment to pompeii, you didn’t ask for this. I may be very critical of myself for many things, but I know that the part of me that whispers, ‘You could have prevented this,’ or ‘You just have to try harder,’ is not the true, thoughtful, understanding part.

        • Ruby, thank you! I’ll write what I meant further when I get the chance to on my blog. And yes, fortunately, I wonder now more than I struggle with the notion. Now that I’ve been in therapy, and that I’ve matured in certain aspects, I’ve learned to be less critical and more compassionate with myself. 🙂 Thanks again for the input.

    • It makes me sad that you struggle some with the thoughts that your disorder is a personality flaw, pompeii. I hope that most days you win that struggle. You certainly didn’t ask for it, any more than someone asks for hypertension or diabetes.

      • I agree with Ruby here.

        As I tell my kids, we cannot change what we have no control over and thus we cannot the past.

        But we do, to varying degrees, have control over the present and the future and can to some degree control how the past influences and affects both our present and future and those of the one’s we love.

        Please know that you are in my thoughts.
        Kind regards,


        • Thanks, Kevin.

          I do shudder sometimes at what has happened in the past – thankfully for me, nothing that destroyed my life or finances. More a case of it coming out of nowhere, with no family history, and then being in full view of quite a few people. But you just have to let it go I guess.

      • Thanks, Ruby.
        I’m definitely better than I was when first diagnosed. I think for me, part of my struggle had to do with finding out what a former manager had said about me behind my back. Which is ironic since she has some sort of physical illness that necessitates her taking time off work to recover when stress aggravates her condition (not sure what it is, she was super secretive about it).
        Thankfully, last year a lovely nurse said almost the same thing as you did about hypertension and diabetes.
        Also, my psychologist reassured me that some of things I struggle with (ie living a healthy lifestyle) are not unique to me. That is, people who do not have bipolar disorder also struggle with these issues. This helped me get over my – ‘oh, I am such a screw up’ attitude 🙂

        • I’m glad you’ve lost that attitude, pompeii. I know firsthand how easy it is to beat yourself up for things that are truly out of your control. But really, all that does is make you feel worse and hinder your ability to healthily process all the aspects of your disorder.

    • I wonder much of the same. There is no solid evidence of BP in either side of my family, though my father’s family does seem to exhibit symptoms. My mother’s family, well, most of them show anxiety symptoms. However, there has to be some kind of genetic link. It’s showing up in distant relatives of my generation.

      So, it makes me wonder the same. But, I can’t imagine why I had the trigger and virtually no one else did. I kind of subscribe to the theroy that if it’s bad enough – however, seeing a doctor in my family is still a sort of shameful thing. They like to hide things, grin, and bear it. For me, that made matters worse.

      Anyone in your family have any substance abuse problems? My mother’s family is laden with alcoholics. It makes me wonder if that’s self-medication.

    • I have learned in my classes that it is a mix of genetics, biology, and enivornment that may be responsible. However, I wouldn’t consider it to be a character flaw. I know, many families, quite like my own, regard my disorder as a sign of weak character – that I couldn’t kust “get over it”. That’s not the case in the slightest.

      You are right about life events that could have triggered it. But, at the time that my BP manifested, my biologically third cousin (whom I call my sister) was not living with us. We are two years apart. And like clockwork, two years later, she was hospitalized for a suicide attempt. This was before her traumatic event happened. Mine was seemingly after I manifested symptoms.

      She and I followed similar patterns. In our teens, we were diagnosed with MDD, and unsuccessfully treated and medicated. But, we have very different personalities. She is shy, and I am generally not. In my mid-teens, I started to get really unhinged, self-medicating with drugs and alcohol up until I became pregnant with my son in my mid-twenties. Her story is hers to tell. Our progression was similar. I was officially diagnosed almost three years ago. She was officially diagnosed almost a year ago. Same progression, different blood line.

      I have a theory. Some people are just better about hiding it. That’s all. It takes an unhealthy amount of control and lies to others, and worse, oneself. I see people in my family that self-medicate. Majority of the women struggle with overeating. Others wrestle with substance abuse and misuse. And it’s all very hush, hush.

      (Believe it or not, a mood can be affected by blood sugar levels. That’s how alcohol works (I’m conjunction with the sedation effect). High blood sugar can temporarily allieviate depressive symptoms.)

      It’s just some food for thought.

      • I don’t disagree that some people are better at hiding it – hell, I was and can still be, when it suits me (which is rarely, anymore). However, I firmly believe that those who hide it also have family who are completely complicit in the denial, for more reasons than I could ever list here.

        They may be ashamed, they may be scared, they may think that they are helping their loved one by keeping the secret. And after a certain point, when an individual has reached their particular “age of reason” and is treating their illness(es) responsibly, if the family wants to keep a secret at the behest of the ill party, “outing them” would be damaging, and a betrayal.

        But I would contend that unless the mental illness in question is extremely mild, or all of the close friends and family are willfully ignorant, mental illness cannot be successfully hidden, not for any length of time.

        And I say this as one who pulled one of the best cover jobs in history on my own parents. But, even they knew at the time, deep down, that something was very, very wrong in my life. They just never forced the issue, because I wasn’t engaging in any dangerous behaviors. And I also do believe there was some denial on their part. Not because they wanted to hide their flawed daughter, but because they couldn’t bring themselves to admit that there was something so deeply wrong inside of me. They didn’t want for me to be hurting like I was.

        And, of course, as loving parents, they felt in some way like they had failed. Like it was their fault that I was ill.

        • That’s the point. Family being willfully ignorant. I am one of those people that has a large circle of “friends”. Except, most are kept at an arm’s length for various reasons, one being to conceal my mental health struggles. And those that I have told in confidence keep secrets well.

          People who knew me before my diagnosis might be able to put the pieces together now. But, most people don’t pay enough attention to make the connection. To them, I was wild, impulsive, and self-destructive. Why? Who knows! It was just the way I was, love it or leave it.

          My family willfully ignored it until it was out there and the evidence was irrefutable. That was only after the medication started working. It’s easy for them to parade me around now. “Look at our daughter, braved Bipolar and won!” Blah.

          It’s a shameful thing in my family. First, people will start assigning blame. Why is she this way? Second, they ask why I couldnt just “be normal” or “get over it”. That’s the part where attention seeking behavior is assumed and weak character is berated. And last, when a person can’t be fixed with tough love, they are ostracized. Because clearly, I’m doing this on purpose.

  6. Manic Monday: “. . . perhaps your mother caught a virus while she was pregnant – who knows?”

    This is something we looked into early on, as I had read about it being a potential cause. Obviously there is no way to know with complete certainty so many years later, but she remembers being quite healthy with me (normal pregnancy sickness notwithstanding).

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