(HealthDay News) -- Though bad behavior may be a typical phase of childhood, certain signs can indicate something more serious.

The U.S. National Library of Medicine says if any of these traits continue for longer than six months, a child may have a behavior disorder:

• Indicating that the child wants to hurt himself or herself, other people or animals.
• Doing damage to property.
• Stealing things or lying frequently.
• Getting poor grades or being truant.
• Abusing drugs, alcohol or smoking.
• Starting sexual activity at a young age.
• Arguing often or throwing temper tantrums.
• Feeling hostile toward people in authority.