One in four adult Americans will have a diagnosable mental disorder at any given time. Frequently, they will have more than one and these disorders could also occur with substance abuse. Typically, people who commit suicide often have a  mental illness that can be diagnosed. Mental health issues are prevalent. Here are the most common mental illnesses. 

The 10 Most Common Mental Illnesses

The term mental illness refers to many different illnesses that could affect a person’s mental health. They can affect how you think, feel, and understand the world. Mental illnesses make it difficult to move through the world, work, go to school, have relationships, and carry out simple tasks. Here are the ten most common mental illnesses:

• Anxiety disorders. This is actually a group of disorders. Included in the group are social anxiety disorder, phobias about certain things, generalized anxiety disorder, panic disorder, and agoraphobia. People with these disorders will often feel exceedingly worried about commonplace situations. You might have sudden anxiety or terror that could culminate in panic attacks. 
• Bipolar affective disorder. Previously known as manic depression, this disorder can cause you to experience extreme mania and depression. You may also have psychotic symptoms. The cause of bipolar affective disorder isn’t known, but some people think that there is a genetic vulnerability to bipolar. If you are stressed, your bipolar symptoms might become more pronounced.
• Depression. A pervasive mood disorder, depression can be diagnosed as major depressive disorder or clinical depression. It can manifest as someone having a sad mood, feeling hopeless, guilty, irritable, or restless. If you have depression, you might have difficulty making decisions, sleeping, or being as productive as you usually are. It may be difficult to eat, and you could have thoughts of suicide or self-harm. You may also feel aches, pains, headaches, or digestive disturbances. Some people with depression experience it in episodes, whereas some people may experience it in a more ambient yet low-level way.  
• Dissociation and dissociative disorders. These disorders are indicated by a lack of connection to your thoughts, feelings, memories, or identity. The experience of dissociation can vary in its presentation and severity. There are transient dissociative experiences and also longer-term dissociation. 
• Eating disorders. These are severe illnesses causing disturbances in how you think of food and how you eat. You may be obsessed with food and your weight. The most common eating disorders are anorexia nervosa, bulimia nervosa, and binge-eating disorder. Anorexia is when you limit how much you eat, and bulimia is when you have periods of restricting your intake then purging it. Binge-eating disorder is when you cannot control how much you eat, and you often have episodes in which you eat far more than you intended.
• Paranoia.  People with paranoia constantly think or feel they are being threatened, even if there is no evidence suggesting danger. For example, you can have delusional thoughts that people or things are a danger to you. In addition, you might have exaggerated suspicions past the point of reason. Paranoia is not a mental health issue in itself but can be a symptom of paranoid schizophrenia, delusional disorder, or paranoid personality disorder, among other disorders. 
• Post-traumatic stress disorder. After a traumatic event, you may develop this disorder. The response can be related to a car accident, assault, combat, torture, or a natural disaster. You could feel intense flashbacks, feelings, or nightmares related to the trigger long after the event has taken place.
• Psychosis. During psychosis, people lose contact with reality, either seeing or hearing things that no one else can see or hear. Psychosis is characterized by having hallucinations or delusions and believing something that no one else believes. Often delusions can be about conspiracies that someone will harm them. 
• Schizophrenia. This is an incredibly severe disorder. People with schizophrenia experience reality in a way that others do not. Typically the symptoms involve hallucinations, delusions, and behavioral changes that make it difficult to function. If you have schizophrenia you can experience severe, rapid mood swings. In one minute a schizophrenic may behave like a giggling child, and the next become very agitated. Schizophrenics may not maintain proper physical hygiene or may lose interest in daily tasks or social life. 
• Obsessive-compulsive disorder. Often known as OCD, those with this disorder are caught in cycles of obsession. You might feel compulsions to alleviate the distress of your obsessions by doing certain rituals or actions. The obsessions are more than just superficial obsessions; they are much more intense. They occur every day and occupy a considerable portion of your life. These types of obsession fill day-to-day life with intense anxiety that gets in the way of properly functioning.