When you go to the doctor for a physical health concern, they may ask you about the symptoms, but they primarily depend on examining or testing the affected area or system.

Although some behaviours and physical indicators (s.a., blood pressure) can be measured and recorded, diagnosing mental health disorders primarily relies on the client's report of their thoughts and feelings during the evaluation. 

As such, exercising selective attention or memory regarding mental health symptoms can complicate this process. Some may even start to express themselves more in line with the symptoms of the mental health issue they believe they have.

For a light-hearted example of how selective attention works, check out this short video.

Just as we tend to focus on one thing to the detriment of others, self-diagnosing based on shared symptoms with someone else's mental illness can lead to hyper-focusing on specific aspects.  It is the difference between the subject you enjoyed in school and the one where the window to the outside looked particularly captivating. I would also wager that you remember a lot more about your favourite subject, while you may mainly just remember how bored you felt.

Likewise, when we self-diagnose based on symptoms we share with someone else’s mental illness, we are susceptible to hyper-focusing on those specific symptoms and not paying attention to others. If you go on to seek help, this can lead your mental health professional to get information that is not representative of the big picture of your emotions, thoughts and experiences. Many mental illnesses share a significant number of symptoms. So, seeking help in this state may provide a skewed view, potentially leading to an incorrect diagnosis or overlooking additional mental health concerns.

Mental illnesses present themselves uniquely in individuals, and while common symptoms exist, personal nuances must be considered before making a diagnosis. The World Health Organization emphasizes the importance of "clinically significant" disturbances associated with distress or impairment in daily functioning.

It's important to highlight the terms "clinically significant" and "distress or impairment." Many of the individual symptoms outlined the Diagnostic Statistical Manual (DSM) could be considered part of the normal human experience. Feelings of anxiety, fear, anger, grief, and sadness are emotions that everyone experiences at some point. However, it is the number and intensity of these symptoms, sustained over a specific duration and within a particular context, that can impact your daily life. This determination of clinical significance helps differentiate ordinary experiences from those that may be indicative of a disorder.