The <a href="[BASEDOMAIN]/healthinfo/BounceLink.aspx?Shortcut=psych" target="_blank">American Psychiatric Association</a> (APA) lists these warning signs of mental illness:
<ul>
 <li>Recent social withdrawal and loss of interest in others. </li>
 <li>A drop in functioning at work or school. For example, quitting sports, failing in school or having difficulty doing familiar tasks. </li>
 <li>Problems with concentration, memory or logical thought that are hard to explain. </li>
 <li>Heightened sensitivity to sights, sounds, smells or touch. </li>
 <li>Loss of initiative or desire to participate in any activity. </li>
 <li>A vague feeling of being disconnected from yourself or your surroundings&mdash;a sense of unreality. </li>
 <li>Illogical or magical thinking, such as exaggerated beliefs about personal powers to understand meanings or influence events. </li>
 <li>Fear or suspiciousness of others, or a strong nervous feeling. </li>
 <li>Uncharacteristic, peculiar behavior. </li>
 <li>Dramatic changes in sleep and appetite, or deterioration in personal hygiene. </li>
 <li>Rapid or dramatic shifts in feelings. </li>
</ul>
If you or anyone you know has several of these warning signs, an evaluation by a mental health professional is in order, says the APA. 
Reviewed 7/3/2023

The warning signs of mental illness

Everyone has different moods on different days, but some changes deserve a doctor's attention. Treatment for mental illness is most effective when started early.