Mental illness refers to a wide range of mental health disorders that affect an individual's thinking, feeling or behavior. These conditions can impact daily functioning and well-being, and may require treatment such as therapy, medication or other interventions. Mental illnesses are common in the general population, with estimates suggesting that about one in four people will experience a mental health disorder at some point in their lives. Some of the most common types of mental illness include depression, anxiety disorders, bipolar disorder and schizophrenia, among others. While there is often stigma associated with these conditions, it's important to recognize that they are treatable and that individuals can recover and lead fulfilling lives with proper support and care.