Exactly.
Warning signs of mental illness:
Recent social withdrawal and loss of interest in others.
An unusual drop in functioning, especially at school or work, such as quitting sports, failing in school, or difficulty performing familiar tasks.
Problems with concentration, memory, or logical thought and speech that are hard to explain.
Heightened sensitivity to sights, sounds, smells or touch; avoidance of over-stimulating situations.
Loss of initiative or desire to participate in any activity; apathy.
A vague feeling of being disconnected from oneself or one’s surroundings; a sense of unreality.
Unusual or exaggerated beliefs about personal powers to understand meanings or influence events; illogical or “magical” thinking typical of childhood in an adult.
Fear or suspiciousness of others or a strong nervous feeling.
Uncharacteristic, peculiar behavior.
Dramatic sleep and appetite changes or deterioration in personal hygiene.
Rapid or dramatic shifts in feelings or “mood swings.”
Source: Psychiatry.org