What are autism spectrum disorders?
ASD, autism, and pervasive developmental disorder (PDD) are labels used for a disability that involves social communication impairment; which label is used depends on whether the impairment is "typical" (i.e. fulfills the criteria for an autistic disorder) or "atypical." Social communication is the skill required to share non-verbal information and is necessary to understand the feelings, intentions, interests, etc. of others. In addition to an impairment in this kind of communication, individuals with ASD have many other problems, such as repetitive behaviours (usually due to sensory processing difficulties) and resistance to change, paired with anxiety and obsession, so often pictured in portrayals of the disorders. See Table 1 for a summary of diagnostic criteria.

Children with ASD and intellectual impairment have a significant delay in verbal language development, while older and higher functioning individuals, for instance with Asperger's syndrome, may be quite verbal. Even people with an intact intellect may display impaired use of pragmatic language and frequently misunderstand sarcasm. Because most people with ASD are intellectually impaired, the term "higher functioning" usually indicates that they're broadly in the range of normal functioning, not necessarily gifted. On the other hand, much of what we know about the condition comes from a few people with ASD who are extremely bright. One example of a very capable person with ASD is Temple Grandin,5 who has a PhD in Animal Science and makes her living designing humane animal handling facilities when she isn't speaking or writing about ASD.

The "spectrum" of ASD isn't all that wide from the perspective of the core disability in social communication: even a "mild" impairment in this area is a serious functional limitation in our increasingly complex social world. It's the additional disabilities (such as the range of intellect) that produce the widest variation in overall function. Just like everybody else, individuals with ASD have a temperament and personality that may alter the appearance of their disability; some are easy-going or passive, while others are more prickly or oppositional.

All people with ASD have difficulties interacting with others; a few are capable of functioning independently, but most require assistance in a group setting. Young children present either with a delay in the communication skills that should emerge during the second year of life, or with the behavioural problems associated with their sensory processing difficulties and/or anxiety disorder. Older individuals may attract attention because of social difficulties or the maladaptive behaviours they use to help cope with social distress and rigidity. Take Tim's and Patrick's cases, for example. Both children have ASD, although they show very different presentations and levels of function. They both have a disorder of social communication that identifies their disability as ASD.

What causes autism?
ASD is usually idiopathic (i.e. associated with no other identified condition), but may also be caused by another disorder. The brain dysgenesis or injury from fragile X syndrome, Down's syndrome, tuberous sclerosis or fetal alcohol spectrum disorder may all produce ASD. For instance, while Down's syndrome usually causes an intellectual disability, it's associated with ASD in about 10% of cases, which makes a big difference in the treatment and outcome.

Although it doesn't often run in the family, ASD is estimated to be 90% heritable6 and caused mainly by "susceptibility genes." The model of susceptibility genetics suggests that we all may carry a small number of these genes, but a larger number is necessary to pass the threshold for the disorder to develop. This may explain the "shadows of autism" or broader phenotype seen in the extended family of those with ASD. The same model is also being used to help us understand a number of other developmental disabilities such as attention deficit hyperactivity disorder (ADHD).

Because there's no definitive information on the genes involved, there are no specific tests available to help a family understand the cause of their particular child's primary ASD. The recurrence risk for the family of a child diagnosed with primary ASD is currently estimated at 10% (remember that the recurrence risk for secondary ASD depends on the underlying condition). Prenatal testing isn't available, and these families often worry for a number of months after the subsequent child is born. Research is underway in Canada to find earlier diagnostic tests.7

A significant minority of children with ASD, i.e. 20% of those with the typical presentation, apparently develop normal communication skills during the first year of life, and then lose them or "regress" during the second year. These kids go on to develop like other children with ASD, but the family is understandably quite anxious about "cause" in this situation. While a child in the middle of a regression should be investigated for potentially treatable underlying conditions, e.g. active or sub-clinical epilepsy or metabolic disease, most of them have primary, i.e. genetic, ASD. For obvious reasons, it's these families who've been most suspicious of vaccinations, environmental toxins, etc. - none of which have shown any evidence suggesting that they contribute.

Should we screen for ASD?
Recent epidemiologic data reveal that although the "core" syndromes of autistic disorder or Asperger's syndrome have remained relatively uncommon at a prevalence around 1/1,000, the broader spectrum of ASD has a prevalence of 6/1,000 (or 1/150), and the male-to-female ratio is 4:1. While there's no evidence of increasing incidence, this prevalence makes it likely that every primary care physician will have several children with ASD in his or her practice. In the crucial period between a child's immunization at 18 months and entry into school, it's the GPs who are most likely to encounter the first symptoms suggesting ASD.

Screening has recently been recommended by the AAP on every well-child visit and at ages 18 and 24 months. Many provincial governments in Canada are starting developmental screening programs. While reliable and valid general developmental screening instruments, e.g. the Parents' Evaluation of Developmental Status (PEDS),8 and screens for early language development are available,9 there aren't any good ASD screening instruments yet. At this time, the Modified CHecklist for Autism in Toddlers (M-CHAT) is the best option,10 and is currently in development. A number of "red flags" to guide surveillance for ASD have been identified and are outlined in Table 2. Additional information about screening can be found on the "first signs" website (www.firstsigns.org) or in the AAP statement.1 Screening tests for adults are also being developed.

When is further assessment required?
Whenever you or the family suspect ASD, further assessment is required. A positive screen is not a diagnosis, and definitive diagnostic assessment is outlined below. All individuals in whom ASD is considered a possibility should have their hearing checked and be seen by a speech-language pathologist in order to connect them with any communication interventions available. Children in the appropriate age group for early intervention or education services should be directed to these, as an intervention worker can both carry out the initial assessment and begin treatment. The question of whether or not to direct families to additional resources about ASD is usually moot, as the majority will already be familiar with the considerable resources of the internet. Many families also benefit from the personal contact opportunities available from their local autism society.

The diagnosis of ASD isn't made on every person suspected, and sometimes a definitive diagnosis may not be made immediately - for both logistic and scientific reasons. While the suggestion that a person may have ASD is often painful for all concerned, it's far better to mention this as a possible diagnosis than to offer superficial reassurance. Most families of individuals with (and without) ASD will already have thought about this possibility, and many report having tried for some time to obtain a referral for more definitive testing.

How is ASD diagnosed?
See Table 3 for the definitive assessment of a person with possible ASD. This kind of comprehensive approach requires a variety of professionals from different backgrounds who ideally have a good working relationship. Some "teams" may see the patient in different places and times and communicate from a distance; in this situation, one person becomes responsible for integrating and interpreting the results of others. School-aged children may have access to a few of the above assessments through the education system, and input from healthcare professionals is required to complete their evaluation. Some of the information needed to sort out the differential may indeed only be available to a general practitioner, such as the family circumstances leading to reactive attachment disorder.

Individuals with typical, severe autism may be "untestable" on standardized tests and extensive assessment may not be necessary to establish their diagnosis. Milder, less typical forms of ASD require more careful evaluation, and young children may need several over time in order to reach a confident diagnosis. This can be difficult for parents looking for intervention, since funding agencies often withhold approval for such programs if there's no clear diagnosis. It's often tempting to offer a more confident diagnosis than the data support in order to get kids into intervention programs, but this approach leads to trouble later on.

One of the major issues in ASD diagnosis is that "neurotypicals," i.e. those of us without ASD, have a range of social communication abilities, and we don't use our skills all the time. While social communication can be precisely measured using research-standard instruments such as the ADOS, in many clinical settings less formal measures (such as the assessor's own ability to interact) are used. People "near the edge of the spectrum" may look more or less functional depending on the environment, so these informal measures are less reliable.

What are the treatment options?
As soon as possible (and often before the diagnosis is fully established), individuals with ASD should begin to work on communication enhancement, behaviour management and family support. The long-term goal of ASD intervention is not to cure the person, but to achieve "optimal functioning." All people with ASD should participate in group learning settings to the extent that they can do so successfully; for some, this may mean a severely restricted setting, while others require only minimal support in order to be integrated with typical peers. The main place that provides group learning opportunities for children is the education system, and this is also the primary location for intervention. Extensive intervention programs such as Applied Behavioral Analysis (ABA) or Intensive Behavioral Intervention (IBI) are also now provided in the family home; they're typically funded through social service agencies, though this varies by jurisdiction.

While there's no specific medication indicated for the treatment of ASD, most people with this diagnosis end up on at least one chronic medication by adulthood; frequently they'll be taking multiple meds, and often these are neuroleptics. The drugs may be prescribed to treat specific target symptoms, for instance sleep disturbances, inattention or impulsivity, obsession or other anxieties, depression or seizures - or they may be for nonspecific problems such as "emotional dysregulation." While medication shouldn't be used as a substitute for good programming and support, it can certainly enhance the effectiveness of interventions (and help retain the support staff) when used appropriately.

For various reasons, individuals with ASD are often treated with a range of alternative therapies. While few of these are actually dangerous, almost none of them have been evaluated, and some have a considerable cost to the family. The potential for guilt trips on the parents' side is also of concern, since many of these "therapies" are very difficult to administer to a person with limited social communication abilities, mistrust of novelty, and sensory hypersensitivities.

Where does the GP fit in?
The primary care physician is involved in many aspects of the care of individuals with ASD and their families. Screening and surveillance are critical, particularly for very young children and adults. Also, families often need support during the time of diagnosis, both to deal with the emotional issues and to gain access to services. Once someone has been diagnosed, they require ongoing care - both for the ASD and for any additional illnesses.

GPs are often the only source of prescribing assistance available and may have lots of experience with some of the target symptoms mentioned. While individuals with ASD may be more sensitive to side effects than others, they usually respond well to the same medications if one "starts low and goes slow." Another obstacle, however, is the resistance to change: the same family that fights the initiation of a medication for months or years may then become extremely reluctant to discontinue it. Support from a family physician is helpful in this.

Adults with ASD face many challenges, not the least of which is that specialist care for ASD is mostly found through pediatricians or child psychiatrists. It's important to have a "developmental" perspective into young adulthood; those of us with young adult offspring know that adolescence doesn't end at 18 - even for neurotypicals. Also, the long-term side effects of medications such as neuroleptics begin to show up later in life. Another difficulty that arises from the transition to adulthood is the problem of aging caregivers and the fact that siblings start to have families of their own. This is yet another "growth opportunity" for family practice.