In the simplest sense, a diagnosis is nothing more and nothing less than someone figuring out what is wrong with you. For some reason, there are only diagnoses for illnesses, never for wellnesses. When you go to the doctor and she examines you and tells you that you are depressed and dispenses some Prozac, you have been diagnosed. If she tells you that you are fine and that there is nothing wrong, you have not been diagnosed.
Mental health doctors don't make up diagnoses. Rather, we get them from a book known as the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Press. This book, known as the DSM-IV-TR (for the forth edition, text revision) is basically a long list of recognized disorders, with chapters on depression, schizophrenia-like problems, drug abuse and dependence, childhood disorders, etc. The DSM-IV-TR is the latest in a long line of previous books that sought to come up with a standardized language for talking about how people can be messed up in the head. While early versions of the DSM were heavily dependent on psychoanalytical theory, these days the disorders it contains have been pretty well scientifically studied. The book gives details on how common each disorder is, at what age it tends to get started, how it tends to affect the people who have it, and most importantly, a list of symptoms and signs that are associated with the disorder. For each disorder, there are important symptoms and signs that must be met before the diagnosis is appropriate to be made. If all the important signs and symptoms are present, the diagnosis can be made. If they are not present, no diagnosis can be made. This tight linkage between symptoms and particular disorder was intentionally created so that one doctor could diagnosis and then a different one treat, but both doctors would understand what was wrong with the patient in the same terms.
The intention of the diagnostic process is to accurately describe what is wrong with someone. If it is possible, the intention is also to link up what is wrong with someone to a known illness causing agent or process. You want to reduce the problem to known illness causing agents, because in order to treat someone, you have to understand what is going wrong. If you can put a good diagnostic lable on someone that accurately describes what is wrong with them, then you have some idea (hopefully) of what has malfunctioned to cause them to be the way they are. If you have an idea what is wrong, then you have a better chance of fixing things (prescribing the proper medicines, therapies, etc. that will "fix" the illness.).
One of the cool things about the approach of the DSM (as a method of standardizing diagnosis) is that it was designed from the ground up to recognize that mental disorders are not just mental disorders. Rather than reducing the description of a particular disorder to mere biological phenomena, the DSM requires doctors to consider the mental (psychological), biological (medical) and social aspects of mental illness. This "BioPsychoSocial" approach is achieved by dividing the diagnosis into five different sections, or "axes". Each axis has it's own roman numeral. I'll describe each of the axes in turn.
Axis I is where a doctor would write down diagnoses such as depression, anxiety, schizophrenia, drug addiction, etc. The diagnoses contained herein are all assumed to be ones that come on if not in (early or later) adulthood, than at least those that develop in someone who was healthy at one time.
Axis II is where a doctor would write down additional diagnoses related to chronic and/or developmental disorders (e.g., types of problems that originated very early in life; there was never a time where the person was "healthy" as defined by the absence of the diagnosed disorder).
Axis III is where information on a person's physical condition is recorded. Information on any significant medical disorders that could be contributing to the diagnosed individuals' stress or symptoms is noted here.
Axis IV is where doctors describe the person's social and economic situation (e.g., their living and working situations, important relationships or the lack thereof, finances, etc.).
Axis V, (the last axis) is a place to record a single number. The number in question (called the Global Assessment of Functioning) is the doctor's best educated guess for how well the person being diagnosed is functioning in the world. The GAF can range between 0 and 100 and provides a way to summarize in a single number just how seriously a person's illnesses are impacting his or her life.
A complete diagnosis might look something like this:
I: Depression, Alcholism
II: Dependent Personality Disorder
IV: Unemployment, Social Isolation
You may have noticed that I've put more than one diagnosis on each of the axes in my example above. This is because, each of the axes can, in fact, have more than one diagnosis on it. This is so that the person being diagnosed can be described as completely as possible. When the first axis (Axis I) has more than one diagnosis on it, a special term is sometimes used to describe the situation. That term is "Dual Diagnosis".
Taken literally, the term Dual Diagnosis is given to a person when they carry more than one significant mental disorder diagnosis at a time. In practical use, it is used to describe those who have been blessed with both a significant mental disorder and a substance abuse diagnosis at the same time. Who are we really talking about here? Well - the population of persons who are depressed, anxious, schizophrenic, bipolar, OCD, etc. who are actively abusing or dependent on alcohol, marijuana, cocaine, heroin or similar opioids, other drugs of abuse, or even illicitly obtained (or sloppily prescribed) 'legitimate' drugs such as Valium and Xanax. There are a lot of these people out there, only many of them are not aware of this fact or don't want to be aware of this fact.
People who are dually diagnosed have a more difficult road to hoe than their single diagnosis brethren. Here are several reasons why.
1. Addictions don't get identified or treated, and the person doesn't get better.
Medicine has been making steady progress in identifing medical chemical treatments for depression and anxiety. One side effect of this progress is that it's become less stigmatizing to admit that you have a problem with depression - it's no longer a moral weakness. But, I think, addiction remains thought of primarily as a moral weakness (even though it is just as biological a problem as anything else). If Depression is now okay to have because it is due to a chemical imbalance, addiction is still viewed as the addicts fault. So people are not jumping out of the woodwork to admit they have addictions. And many physicians and other clinicians are not fully savy about dual disorder problems and so focus on the treatment of what seems to be primary (the mental illness/depression/anxiety part), while relatively ignoring the addictions part.
Ignoring the addictions part when it exists, however, is a really big mistake for several reasons. The presence of drugs in a persons system can sometimes interfere with the action of corrective medicines such as anti-depressants, rendering these needed medicines less- or not at all effective. Even worse, persons who are addicted to drugs often have trouble staying organized as their lives become increasingly oriented around obtaining more drugs. This disorganization makes it hard for them to stay on a regular pattern of daily medication. In some cases drugs of abuse contribute to - even help cause mental illnesses. Depression, for example, can be induced by drinking alcohol which is a depressant drug.
Persons whose addictions serve self-medicating purposes can be reluctant to talk to their doctors about their addictions for fear that the doctor will tell them to stop drinking or drugging. For instance, the anxious alcoholic might be reluctant to disclose the full extent of drinking taking place. Addicts comming off of alcohol and other anti-anxiety drugs experience severe anxiety as a function of physical withdrawal from the alcohol - they don't want to feel this way and so are further motivated to hide their drinking from their physician.
2. What works to treat either a mental illness alone, or a drug addiction alone, doesn't work quite as well for treating Dual Diagnoses at the same time. (Dual Disorders need special care)
Those dually diagnosed persons who do get into treatment for their drug addictions often find that the support they need is not quite all there for them. For instance, the AA organization and other similar 12-step programs are designed primarily to treat persons with addictions. The members of AA (bless them all) are zelous in their pursuit of sobriety, and don't always know when a drug is part of an addiction and when it is part of a legitimate medication regime. It is not uncommon for a new dually diagnosed participant in AA to be told that they must cease taking ALL drugs if they want to become sober (including prescribed medicines needed to treat mental illness conditions). This of course is confusing to the dual diagnosed patient who is told to be on the medicines by his/her doctors and to be off them by his/her sponsors. This sort of stress is not helpful.
To AA's credit, there are more and more "dual diagnosis" meetings for people to attend. There are also (at least in larger communities) often one or more treatment facilities that are sensitive to the special treatment needs of the dually diagnosed patient. Look for such a resource in your community if you need one (or find a social worker type person, perhaps through your local community mental health center - he or she will be able to point you in the right direction.
There is, of course, a whole lot more that can be said regarding these issues. But I thought that this would be useful information to get out there to folks who can benefit from it. Thanks for asking.
Dombeck, M.J. (Nov 2000). Diagnosis and Dual Diagnosis [Online].