One of the difficulties of reading the early warning signs of schizophrenia
is the easy confusion with some typical adolescent behavior.  Schizophrenia
can begin to affect an individual during the teen years, a time when many rapid
physical, social, emotional, and behavioral changes normally occur.  There
is no easy method to tell the difference.  It’s a matter of degree. 

If you have any concerns, the best course of action is to seek the advice of a
trained mental health specialist.
The following list of early warning signals of mental illness was developed
by families affected by schizophrenia:
Most Common Signs

• Social withdrawal, isolation, and suspiciousness of others
• Deterioration and abandonment of personal hygiene
• Flat expressionless gaze
• Inability to express joy
• Inability to cry, or excessive crying
• Inappropriate laughter
• Excessive fatigue and sleepiness, or an inability to sleep at night
  (insomnia)

Other Signs

• Sudden shift in basic personality
• Depression (intense and incessant)
• Deterioration of social relationships
• Inability to concentrate or cope with minor problems
• Indifference, even in highly important situations
• Dropping out of activities (and life in general)
• Decline in academic or athletic performance
• Unexpected hostility
• Hyperactivity or inactivity, or alternating between the two
• Extreme religiousness or preoccupation with the occult
• Drug or alcohol abuse
• Forgetfulness and loss of valuable possessions
• Involvement in auto accidents
• Unusual sensitivity to stimuli (noise, light, colour)
• Altered sense of smell and taste
• Extreme devastation from peer or family disapproval
• Noticeable and rapid weight loss
• Attempts at escape through geographic change; frequent moves or
  hitch-hiking trips
• Excessive writing (or childlike printing) without apparent meaning
• Early signs of migraine
• Fainting
• Irrational statements
• Strange posturing
• Refusal to touch persons or objects; insulation of hands with paper,
  gloves, etc.
• Shaving head or removal of body hair
• Cutting oneself; threats of self mutilation
• Staring, not blinking, or blinking incessantly
• Rigid stubbornness
• Peculiar use of words or language structure
• Sensitivity and irritability when touched by others 
• Change of behavior: dramatic or insidious.

None of these signs by themselves indicate the presence of mental
illness.  Families who helped compile this list have indicated that they
unfortunately had not acted on these early warning signs.  With the benefit of
hindsight and today’s knowledge about early intervention, family members are urged to
seriously consider seeking medical advice if several of
the behaviors listed above are present, or constitute a marked change from
previous behavior, and persist over a few weeks.