Schizophrenia mostly starts around 19 -21 years of age. Despite that, it can begin in early childhood. In that case, it's referred to as "Childhood Schizophrenia". Symptoms are fearfulness, withdrawel, emotional unresponsiveness and auditory (or otherwise) hallucinations. In cases where Schizophrenia starts much later, some of those affected showed signs of mild autism and moodiness in childhood.
Asperger's is thought to start around aged three. It's recognised by motor clumsiness (useless at ball games). There is poor emotional intuition and connection to other people. There are major difficulties in group, class education. These children switch off and daydream in class. Yet, they develop obsessive interests in obscure subjects and are avid readers. They strive to keep their surroundings the same and follow fixed routines. They may have explosive outbursts.
How do you know if a child has Asperger's or Schizophrenia? The principal difference is that Asperger's remains stable in its symptoms. The problematic pattern remains constant. Yet, with Schizophrenia, there are "swings" where the symptoms intensify. Followed by further changes in behaviour. Often, the swings manifest outbreaks of fear and foreboding or hallucinations. For me, during childhood, it was audible sounds of breathing in the bedroom, or electrical humming. Hiding in cupboards or behind doors. Terrifying nightmares and floating sensations. Asperger's normally lacks "change" or sudden worsening of symptoms.
Another crucial point is that Schizophrenia changes and develops. Whereas fear and withdrawel defines the initial stages of Childhood Schizophrenia, much later in life the predominant mood is total apathy. There is weak, emotional response, couldn't care less, low motivation and physical activity. Whereas, Asperger's remains the same.
The big problem I have is both apply. Usually, Schizophrenics don't have motor clumsiness yet, if you were to neet me in person, straight away you would notice. Stiff, slow, cumbersome movements like Rain Man. I can"t catch a ball. Special interests also applied from childhood. Sensitivity to fabrics applied, as well as learning difficulties.
Really, the experts never fully agreed. Still, Schizophrenia can initiate in childhood and, if it does, it will differ from Schizophrenia that starts in later life.