In January, after many years of inaction, British medical regulatory officials finally found Dr. Andrew Wakefield guilty of unethical behaviour in carrying out research that, he claimed, showed a connection between the measles-mumps-rubella (MMR) vaccine and autism. Soon after, The Lancet issued a full retraction of Dr. Wakefield’s 1998 paper, turning the page on an ugly chapter in the journal’s recent history that saw most of the coauthors disavow the autism/vaccine theory. That theory, already shown to be unsupported by the evidence in large studies, truly no longer holds water. So what actually causes autism?
We asked Jeanette Holden, PhD, program director of the Autism Spectrum Disorders - Canadian-American Research Consortium (ASD-CARC), to describe the latest science on autism’s etiology. Dr. Holden, who studied genetics with David Suzuki, is also a professor of psychiatry and physiology at Queen’s University and sits on the board of Autism Society Canada.
PE We know it’s not vaccines, so what are the current ideas about what causes autism?
JH It’s quite clear there are two components to all complex disorders -- diabetes, asthma, and so on. Autism is no different. Both genetics and the environment play a role. We know genetics is critical because when you look at a number of patients you often see something very similar to autism, or at least that has some of the components of it. We call that the broader phenotype . That is, there may be some of the social problems and some of that rigidity, almost that one-track mind, the ability to concentrate on something. We see that often in families. Hyperactivity is common in families with autism. Quite often there’s depression in the family. When you start to see a clustering of underlying similar conditions, you really do have to think that genes are somehow involved here. There have been a lot of discoveries in the last few years of specific chromosome changes that happen. It’s not the same change in everybody, but a lot of different changes: small deletions and duplications, or copy-number variants. So there is definitely this genetic component, but we don’t know about factors within the environment -- chemicals or something in our diet -- that might also be contributing to this, and that is going to take a long time to sort out.
PE You mentioned chemical exposure and diet as possible environmental factors.
JH I wouldn’t be surprised. Cancer rates are higher. Asthma is out of this world. You see asthma a lot in autism as well. Is there some kind of a connection there? Similar environmental agents that are causing it? I don’t know. Certainly part of our research is to look at all kinds of comorbidities and other conditions that are present in people with autism spectrum disorders or in their families, because that might give us a clue as to the cause and the etiology in that family. I mean, I have acute myelocytic leukemia, which shocked me. Every time I think about it, I think, “Gee whiz. Of all the things I might have as I age, this is definitely not one I would have thought of.” I worry about what is that I have been exposed to. When I talk to people I don’t know, they see my short hair and they ask me, and they’ve got relative with AML or acute leukemia of some sort. There just is so much of it. And it’s a very rare kind, multiple myeloma. I have a friend whose husband passed away with this. And just last week I was talking to somebody whose uncles has it. I should not be connected in some short way, like an n of 4 between us, to other people with it. It’s that rare. It shouldn’t happen, but yet it does happen. You start to wonder.
PE Wakefield suggested a connection between autism and intestinal disorders, even though he wrongly attributed the digestive problems to the MMR vaccine. Could there be something there?
JH The study hasn’t been done but I think there could very well be. You could imagine that if a child has some kind of bowel disorder and is in a lot of pain, then their behaviours might be very much autistic. We have to remember that autistic behaviours are symptoms. They are not the disease. We just have to figure out what the basis is for these behaviours. Is this a neurological disorder? Is it something to do with pain? Is it an auditory processing defect? What is the root of these behaviours in a particular individual? That’s the way we have to go in future. I don’t think everybody believes that. A lot of people feel it’s a mental disorder and I am not convinced of that. I think a lot of the behaviors come from the struggle to communicate. For example, you will often hear people saying they [autistic patients] are aggressive, and I have often seen my autistic brother get aggressive when he’s frustrated. When he has normally been able to get his message across to people and suddenly he can’t. He needs time and people are very impatient. We are all very impatient. We finish each other’s sentences. Two people talk together at the same time and somehow carry out a conversation, even with overlap. When you have a group of three people, two people talking is not all that uncommon -- we find that all the time. You know, people try to look at signals but we get so engrossed in things that we want to get it all out and we seem to have something more important to say than the next person does, so we blurt things. Conversations are not necessarily the I-take-a-turn-then-you-take-a-turn types of things, and a person with autism is trying to follow this conversation. And if they can’t finish a sentence or they can’t finish it quickly enough, suddenly they get upset, like my brother. But it might not be his problem. They problem is he can’t quickly enough interact and he is just trying to signal something to people and they don’t understand it.
PE And you believe that auditory processing problems could be one of the more important things that doctors are overlooking in autistic patients?
JH I think so. It’s really clear in my brother, who is autistic. I just can’t imagine what it must have been like for him. I try and it’s painful, because his auditory processing problem was not identified until he was 47. Can you imagine what he could have learned if we’d been aware of this when he was five, and how different his life would have been? That’s very painful. Very, very painful. But at least we didn’t learn that when he was 60.
PE Do you subscribe to the school of thought that says the prevalence of autism has actually risen over the last 20 to 30 years, or do you think there is simply more awareness, and therefore more diagnoses, now?
JH A lot of it is awareness, but I think there really is an increase. I don’t know how big, but there is probably some increase. We’ve got so much more now we didn’t have before. We have computers. We have kids that learn to use computers when they’re two! And that’s a very isolating world: put a child in front of the computer and let them play by themselves? The big question is whether the computer is taking that person who would be on that broader spectrum but managing okay, and therefore you then have a child that is not on the broader spectrum but is now on the autism spectrum because they have restricted interests, because they spend a lot of time away from other people.
PE What do doctors need to know more about when dealing with autistic patients?
JH I think knowing that these behaviours, the difficult behaviours, are because a child is trying to communicate when they’re nonverbal. Even with verbal children, they may not have the skills to say something meaningful. A person with autism doesn't have to have these outburst behaviours. I think, letting families and physicians know that there is a reason for the outbursts and that you have to find what that reason is to prevent them - that you can prevent them. That is the most important thing.
PE Where do you think research about the causes of autism is headed?
JH It really requires an interdisciplinary approach. That is what our research team is all about, putting everybody together -- the psychologists together with the neuroscientists, geneticists with the physiologists. You need to put all of these things together to get a comprehensive picture of the individual and their families. And subgrouping. When people were studying patients who were labeled mentally retarded, we never would have learned the cause of Down syndrome if we hadn’t taken a group of individuals and looked at the physical similarities between them and then looked at their chromosomes. If you’d just had, say, a random sample, or a consecutive sample even, of individuals with an intellectual disability and looked at their chromosomes, you might have found just one person with trisomy 21, one person with fragile X syndrome, another with Prader-Willi, you probably wouldn’t see the abnormalities necessarily in the chromosomes or maybe you should, but it would look like three different abnormalities and nothing to do with the mental disability itself. So you’d say that these are interesting findings but they don’t tell us anything. What one needs to do is say either we look at people’s physical differences or characteristics in the family and separate out individuals according to those characteristics. Or you do genetic tests on a large number of individuals and you find, oh, well, in one percent or half a percent they have this particular chromosomal abnormality. That might be a new syndrome. Or not even half a percent -- maybe it’s in a very small proportion of individuals. You start to find something that’s maybe found in 10 people in the world. With more awareness by doctors, there’s a lot more recognition then of that. We found two individuals with the same overlapping chromosomal abnormality -- a new syndrome -- and once that was published, other people started finding it as well, and parents contacted us to say their child has been identified with this and now they’d like to know more about it. With more information about a syndrome, we know what to watch for. With Down syndrome we know we have to watch for Alzheimer’s as they get older. Well, you wouldn’t know that if you only studied young children. But as long as you study a large enough group and you follow them through the life span, you start to pick up things that are indicators of perhaps early Alzheimer’s or a thyroid condition, hypothyroidism, which is also common, depression, a number of things you start to characterize that syndrome by.
PE Do you feel that that kind of interdisciplinary approach to studying autism has helped make progress in the study of autism?
JH Yeah. I don’t think we could do it without that. I work really closely with clinicians and psychologists as well. It takes a while to convince some psychologists there’s a genetic component here because a lot are really thinking only about behaviour, but I think they are becoming much more aware that there could be different reasons for behaviors, which is not what is typically believed by psychologists.