On an anecdotal level, I’ve seen the full spectrum while working at a hospital that draws patients with borderline disorder from all over, but in particular, we manage all acute psych services for students at Harvard and MIT students. Of those students, I‘d estimate 25% of the girls/women who are treated on inpatient across the hospital arrive or leave with a BPD dx (there’s 9 separate units with 7 differing classifications, so it ranges from 0% on the geriatric units to 90-100% on the women’s trauma unit) and those girls/women are universally high IQ. Then there’s a self-pay (out of reach pricing for middle, even upper middle class families to pay for) residential program at the Gunderson Center, which was developed by Dr Gunderson and specializes solely in treating females with BPD and a majority of those patients have at minimum slightly above average IQ. On the other hand, the inpatient units accept Medicaid/MassHealth, so we often see pt’s with average IQ’s at best, so based on the sheer volume of patients I’ve come in contact with, I’m relatively confident there’d be research to support either position (+/-100 IQ average). Where I you’d see the serious deficits would almost certainly be in emotional intelligence and cognitive regulation testing, so the Metacognition Assessment Scale (MAS-A) would really provide a better window into the overall picture of a person’s actual cognitive function at that time. IQ-wise, I believe it’s a pretty broad spectrum though. As a disclaimer I’m a relatively new (and only master’s, not PhD level) clinician and not an “expert” or researcher, so it’s possible I’m incorrect due to the high cost of the residential program at the hospital I work, the connection with the previously mentioned universities, as well as a location under 10 miles from downtown Boston and all it’s other major universities Providing a pretty high IQ population across diagnoses. I probably could have made this response shorter, so apologies if I rambled on.

Considering that increased extracellular dopamine increases learning and attention and Borderlines do many things that increase dopamine including drugs and about 70% of Borderlines use drugs at some point, then my guess is that a high number will have above average IQ (excluding the small % born with learning disabilities).

Since many of the things they do increase dopamine (i.e. drugs, cutting spending, gambling, hoarding, etc) then that tells me that BPD is a hypodopaminergic condition. perhaps like Reward Deficiency Syndrome because all the behaviors associated with it are exactly the same as in BPD (hyper sexuality, sadism, nasochism, disinhibition, self harm, tricotillomania, skin picking, body dysmorphic, etc).