Autism Spectrum Disorder (ASD) is classified by the CDC as "a developmental disorder caused by differences in the brain." Sometimes, these differences are known - such as a genetic condition. Other times, however, it is unknown. Even though scientists believe there are multiple aspects of a persons life that all act together to change common development, there are still a lot of unknowns about ASD.
People living with ASD often behave, learn, communicate, and interact with others in ways that are different from most people. There is usually nothing about the way someone looks that can tell you whether or not they have autism. It can have a variety of effect on people diagnosed - for example, some folks are completely non-verbal while others communicate just fine, and some people with ASD need a lot of help in their daily lives, while others do not need the same assistances. This is because Autism isn't a cut and dry, black and white type of diagnosis - it is a scale, and a spectrum.
Signs of Autism usually appear before the age of 3, and will last throughout a persons life - although some symptoms may improve over time. Children with autism growing into teenagers, and into adulthood, often find themselves struggling with communicating with their peers, developing friendships, and understanding social queues for behaviors expected at work or school. This can go hand-in-hand with other mental health issues, such as anxiety, depression, and ADD/ADHD (Attention Deficit/Deficit Hyperactivity Disorder) which are all more common in those also living with Autism.
But what are the signs?
There are a lot of behaviors that can categorize Autism, but also categorize a wide variety of other disorders and mental health situations. Because of this, it can be complicated to diagnose with 100% certainty - especially if the Autism symptoms are the same as other symptoms, such as aspects common with ADHD.
Some common signs of autistic behavior:
Does not like/use eye contact, or avoids it all together
Unable to notice when someone is hurt or upset around them
Incapable of picking up social queues, seems to be living in their own little world (not antisocial, just missing the queues)
Factual, instead of imaginative (this is not to say that people with ASD are not extremely creative)
Repetitive/Restricted behaviors and interests (obsessive routines, repeats words or phrases, flips hands or rocks body in a physical 'stim', gets very upset with minor change)
Some other characteristics that can come into play:
Delayed language and/or movement skills
Delayed cognitive/learning skills
Unusual eating or sleeping habits
Hyperactivity, aloof behavior, impulsivity
Unusual mood/over-emotional reactions
Gastrointestinal issues (constipation is common)
Anxiety, stress, excessive worry
Extreme fear, or complete lack of fear
How do I know if it's ASD or something else?
Diagnosing Autism Spectrum Disorder can be very challenging, because there's no quick and easy test to take to get the answers. We cannot take blood and run it through a lab, or a cheek swab in some solution - instead, in an ideal world where the diagnosis is successful in childhood, a licensed medical professional will pay attention to all the behaviors and developments your child has gone through thus far.
Though ASD can show up as early as 18 months, normally a diagnosis isn't concrete until the child is between 2-3 years old. But since your doctors can't live in full time and watch your child's growth and behaviors, parents and family often have to participate in something called Developmental Monitoring. Developmental Monitoring is exactly what it sounds like - keeping an eye, making note, and paying close attention to your child. Should we compare our children's hobbies and likes? Of course not. But if your 2 year old is in daycare, and the rest of the children can sing and wave and your child cannot, this is something to take note of.
In finding a correct diagnosis, medical professionals will also suggest Developmental Screening appointments. This is much more formal than Developmental Monitoring, and the American Association of Pediatrics suggest that all children undergo Developmental Screening at 9, 18 and 30 months. These tests will usually be rolled in with normal wellness visits, but during the 18 and 30 month visits are when medical professionals add in additional screening for chances of ASD.
Signs for autism in adults can be just as dramatic as they are in childhood, but can also be less intense. There is also a difference between men and women, as adults, experiencing Autism. Women suffering are often times quieter, and quicker to adapt to social situations although they may be internally suffering greatly. Due to their natural desire to swallow their feelings (due to other societal/cultural expectations), diagnosing adult women can be much harder than their male counterparts.
Since some patients are never diagnosed in their childhood, or misdiagnosed with ADHD (reflecting some autistic behaviors), the safest bet is to talk to your primary care and get a referral for testing if possible! It's better to know the full span of your brain, so that you can take the best care of yourself and live the life you deserve.