So, you've seen your general practitioner, and then a psychiatrist, and now a counselor. You thought this was supposed to help, but instead they have managed to all tell you something different about your diagnosis! This is supposed to help, not make you more confused! Why does this happen? Well, there are a couple of reasons...
Differences in Professions
Most medical professionals use the ICD-10 while mental health professionals such as psychiatrists, psychologists and counselors use the DSM 5. I could go into what exactly they are and the differences therein, but it would bore you, and me, so we won't. Instead, I'll just tell you they are different. The differences are not huge, and the implications from a patient's perspective is about names. The inside professional arguments are arcane and full of a lot of turfism, but suffice to say that if your doctor says ADD and your counselor says ADHD, it's not likely going to be a difference beyond terminology.
Differences of Opinion
Yes, we disagree. We have our own biases, our experiences, and our perspectives. These experiences color the way we look at information, and so will lead us to somewhat different conclusions. This can be very frustrating as a patient, as it leads to one person telling you one thing while another says something completely different. I wish I could give you a magic formula to stop that, but it just does not happen. That said, I will suggest that you challenge these professionals in their diagnosis. If one says ADHD and the other says Bipolar disorder, challenge them: why did they choose what they did? Why not something different?
Difference in Information
You are the source of information used to arrive at a diagnosis. Your doctors, counselors and the like are trained on how to interview you so we can get more information, but the reality is we are not all knowing. This may surprise you, I know, as you have that counselor who acts like he does know everything. But really, they do not. We need you to tell us what is going on, and if we do not have complete information, it will not be an accurate diagnosis. You may share a detail with one professional but not another, and so they arrive at different diagnosis. You may have a long history with one of them, who has picked up lots of minute details over the years, so her diagnosis may be more accurate than the person you just met. It all takes information.
Oh yeah, I went there. Some professionals are just incompetent. My father is a medical doctor, and is fond of quoting a common saying from medical school, "You know what they call the person who graduates the bottom of his class from med school? Doctor." This applies to Counselors, Psychologists, and Marriage and Family Therapists as well. That tells you some are not the sharpest tools in the shed. Some are just bad. Others, though, are great at what they do, so figuring out which is which is key.
One way to watch out for incompetence is to keep any eye on some of the "easy out" diagnoses. You have heard them, maybe even believe they are made up things due to how casually they are thrown about. ADHD comes to mind, with it's massive uptick in diagnosis in the 90s. Yes, ADHD exists, but no not every child you cannot sit still does so because their brain is unable to regulate them properly. Bipolar disorder is another popular diagnosis to slap on someone. There's also a rise in Post Traumatic Stress Disorder being routinely applied to everyone that has ever had anything traumatic happen. The reality is, these diagnoses are real and hard, but your doctor, psychologist or whoever should be able to point to specific symptoms in detail and explain how they have it. Not, "Well, they get angry, really angry." Or "well, they experienced trauma." Those are not enough to make a diagnosis. Those diagnoses are very real, but to make the diagnosis requires actual information and real distress.
Another sign to watch out for in regards to incompetent diagnosis is what I call "the diagnosis stack." Many diagnoses can be co-morbid, meaning they can occur at the same time as another, but some professionals take this to an extreme. ADHD and Oppositional Defiant Disorder don't raise my eyebrows. But when I see something like: ADHD, Bipolar I, Conduct Disorder, Oppositional Defiant Disorder, Intermittent Explosive disorder all coming from one clinician, it makes me very skeptical. First, because some of those cannot be co-morbid. Second, there's a point where there is so much going on symptom wise with just two or three disorders that distinguishing more symptoms as their own diagnosis seems far fetched. There's just to much going on to really be firm about that.
What to Do About it?
There are some techniques you can use to weed through incompetent diagnosis. One such technique is the above advice in asking for justification of the diagnosis. Your psychologist or whoever you are seeing should feel confident enough in their diagnosis that they can withstand some questioning. You do not have to be rude or angry about it, but they should be able to answer you and be able to defend the disorder, and make you feel confident they are on the right track.
Another technique is to ask one professional about their thoughts of the other diagnosis. A good counselor or psychologist should be able to look at the other person's diagnosis and be able to give you a reasonable approximation as to why there could be a difference. It is a common enough thing, and the differences in both perspectives and professions is enough to have an honest conversation.
This final thing is to ask the "what now?" question. This is why we have a diagnosis: What are you going to do about it now? If your professional gives you some mealy mouthed answer, it tells you he or she doesn't know what they are doing. If they tell you they have to devise a treatment strategy, that's fair, but don't let it become an evasion. Now that they have a diagnosis they should have a plan of attack.