All the people I have ever met with Bipolar Disorder also had SPD. In fact, sensory inputs triggered some of their Manic and Depressive swings. I had to learn to not bring food that contained Vinegar to one friend's house because it would set off a Manic episode.

I don't know the best way to explain it to doctors or psychiatrists. I have better luck with Nurses for some reason.

I just explain that my senses were overly sensitive and minimal environmental changes can cause an overloading of my brain putting me in Fight or Flight mode.

My body overreacts to the adrenaline rush from the "Fight or Flight mode" and triggers a paralysis attack (I have Hypokalemic Periodic Paralysis), because adrenaline binds with the available Potassium in your blood stream and can make it unavailable for your muscles. Since I have Hypokalemic Periodic Paralysis, even the smallest drops in available Potassium puts me at risk for a paralysis attack. Normal people take large drops in Potassium before they have problems (sustained adrenaline usage for hours in a normal person could cause a similar effect to one of my weakness/paralysis attacks).

As you can see, I tend to either get the "you're crazy" look or "you're too complicated for me" discussion. Getting the "you're too complicated for me" discussion from the top of the profession researchers and Neurologists is incredibly depressing.