If you are interested in finding further information about particular psychological topics, these may be some good places to start. 

Many people have difficulty coping with stress, anxiety or trauma, and there are a variety of ways that these problems may be manifested. Often, Anxiety is actually a symptom of Depression, and when depression is treated, the anxiety can relent, especially when the anxious feelings occur only in the presence of depression. However, there are times when the Anxiety is simply that. For example, Acute Stress Disorder is difficulty coping with a traumatic episode in the immediate aftermath, while PTSD, or Post Traumatic Stress Disorder, is a more chronic and debilitating problem coping with a disturbing event which was witnessed, experienced, or vicariously experienced through others to a distressing degree. You may want to visit the  National Center for PTSD.

When the anxiety is primarily experienced socially, the diagnosis to rule out is Social Anxiety.

        OCD, or Obsessive Compulsive Disorder, is another common manifestation of anxiety. There is a national Obsessive Compulsive Disorder Foundation, which can be helpful to people struggling with these symptoms.

Many people have difficulty coping with stress, anxiety or trauma, and there are a variety of ways that these problems may be manifested. Often, Anxiety is actually a symptom of Depression, and when depression is treated, the anxiety can relent, especially when the anxious feelings occur only in the presence of depression. However, there are times when the Anxiety is simply that. For example, Acute Stress Disorder is difficulty coping with a traumatic episode in the immediate aftermath, while PTSD, or Post Traumatic Stress Disorder, is a more chronic and debilitating problem coping with a disturbing event which was witnessed, experienced, or vicariously experienced through others to a distressing degree. You may want to visit the  National Center for PTSD.

When the anxiety is primarily experienced socially, the diagnosis to rule out is Social Anxiety.

        OCD, or Obsessive Compulsive Disorder, is another common manifestation of anxiety. There is a national Obsessive Compulsive Disorder Foundation, which can be helpful to people struggling with these symptoms.

Depression is perhaps the most common psychological concern, especially when depression-related anxiety is included. The CDC estimates that 1 in 10 Americans experience depression. Of course, everyone feels depressed sometimes, but there is a difference between a "normal" depression which is an understandable response to difficulties and more serious depression. True depression is a serious and potentially life-threatening condition and should not be ignored. Symptoms may include sadness OR loss of pleasure in activities you usually enjoy, in addition to weight loss or gain, fatigue, irritability, insomnia or oversleeping, feelings of guilt/worthlessness/hopelessness, and thoughts of death or suicide. These symptoms should not be ignored, but treatment can help. Research has shown that the most effective treatment for depression is therapy combined with medication. For further information, see this article by the CDC.

Depression can also be a symptom of Bipolar Disorder. With Bipolar Disorder, periods of depression alternate with periods of manic behavior in which a person may find themselves highly energetic (often needing little sleep) and behaving much more impulsively, taking more risks, feeling more grandiose or more irritable and angry. Bipolar disorder is a serious illness and requires medical treatment. 

AD/HD is currently the sanctioned title for what was once called ADD and ADHD. There are three subtypes of AD/HD: 1. Hyperactive Type (more common but not exclusively found in boys), 2. Inattentive Type (more common but not exclusively found in girls), and 3. Combined Type. Contrary to once-held beliefs, most people do not grow out of AD/HD as they age, but they do usually become more adept at finding and using strategies that take the best advantage of the unique gifts that their brains have to offer. People with AD/HD tend to be intelligent, creative, out-of-the-box thinkers who are often misunderstood as unmotivated, when they can actually be highly motivated individuals who simply need to adapt their environment or themselves. If you or your child has difficulty focusing or concentrating (EXCEPT on things that are highly interesting), often neglects to finish tasks, frequently forgets or loses things, or has other symptoms, you may want to take a closer look at the other symptoms of AD/HD here. Adults are often diagnosed as a result of the process of getting help for their children. Find help from CHADD for adults, children, and parents  or for adults here. AD/HD cannot be cured, but many find that with effective strategies and/or the right medications, that they are able to flourish. 

If you are concerned about addictions, the US government department of Substance Abuse and Mental Health Services Administration  has links to helpful information on suicide, substance abuse and nicotine addiction.  In addition, you may want to check out  Alcoholics Anonymous or Narcotics Anonymous. Here are links to Sex Addiction articles and self tests, as well as the Center for Internet Addiction.