F99: Mental disorder, not otherwise specified

Mental disorders, not otherwise specified (NOS), refer to a range of mental health conditions that do not fit into specific categories defined by psychiatric classification systems. They typically involve symptoms affecting the patient's thinking, feelings, behavior, and overall well-being, to a far greater degree than ordinary day-to-day variations in mood or behavior. The causes of these disorders can be complex and varied, often including a mix of genetic, environmental, and psychological factors. Some patients may present with symptoms of multiple disorders that can't be distinctly diagnosed. While the precise nature of NOS mental disorders can make them challenging to diagnose, they generally exhibit some form of clear clinical distress or impairment in social, occupational, or other important areas of functioning.

Patient Disclaimer

The information provided on this page is for general educational purposes only. It is not intended for self-diagnosis and does not replace professional medical advice. Always consult your doctor or a qualified healthcare provider with any questions or concerns about your health.

If you see an ICD diagnosis code (e.g., on a medical report), be aware that doctors may also include additional indicators to express diagnostic certainty. Only a healthcare professional can interpret these codes accurately in the context of your individual case.

For a complete understanding of your condition and what the diagnosis means for you, please speak directly with your doctor.