A Clinician’s Guide to Differentiating ADHD and Borderline Personality Disorder

Fear of abandonment can cause people with BPD to misinterpret situations or events where no real rejection or lasting separation has taken place. They may become upset or angry, for example, when a friend is a few minutes late in meeting them, thinking that the friend is trying to avoid them.

BPD may cause people to engage in elaborate and desperate behaviors in a bid to hold on to their relationship(s), especially their romantic relationships. At the same time, people with BPD might experience difficulties connecting in those relationships.

Because many people with ADHD have a very hard time entertaining and stimulating themselves, they may seek and find stimulation in social interactions. Engaging with others can make the bored ADHD brain feel present. Under-stimulation may lead to desperate bids for connection.

If a patient with ADHD is properly stimulated, they likely will not engage in frantic, desperate efforts to hold on to people. They may not even experience great concerns around abandonment.

People with BPD tend to engage in dichotomous thinking. They often perceive themselves and others in terms of good and bad, perfect and imperfect, being all in or all out, and other extremes. This tendency causes problems in interpersonal relationships, especially during dating and in early romantic relationships. The individual with BPD might view their partner as the hero of their lives — the be-all and end-all. Everything about their partner is perfect — until it’s not. Then, everything about that partner is awful.

This black-and-white, all-or-nothing pattern of thinking makes it difficult for people with BPD to connect and relate to others. At the same time, existing in the middle is often difficult for people with BPD. Navigating gray areas in relationships means trusting themselves and others, which is impaired in BPD.

People with ADHD may idealize their romantic partner and relationship during the honeymoon phase, when the newness of the relationship excites and stimulates their dopamine-seeking brain. As routine sets in, so does devaluation in some cases. The person with ADHD might think, “I don’t like this person as much because they aren’t engaging me enough.”

Interpersonal problems associated with ADHD are common but seldom as severe as they are in BPD. Many people with ADHD have strong, positive relationships.

Sense of self is markedly and persistently unstable in BPD. There may be sudden, dramatic shifts in goals, values, opinions, types of friends, and other parts of identity.

In many ways, people with BPD may try to gain a sense of self through relationships. They may affiliate themselves with someone they idealize and, by extension, begin to see themselves as “good.” Sense of self is also malleable and based upon where the individual with BPD thinks they will receive the most love, validation, and/or acceptance. This often results in unstable interpersonal relationships.

People with BPD also often describe feeling as if they don’t exist, especially when they are alone. In this way, being in the presence of others helps validate their existence. (See symptom #1.)

A healthy sense of self and identity (which most people develop) is like a fully formed key. For people with BPD, this key is either not fully formed, or its design is ever-changing, based upon the lock the person is trying to fit into at a given time.

Executive functioning and maturity delays, for example, are common in ADHD and may affect self-perception and the development of identity. This may explain why many adults with ADHD feel they haven’t achieved full adulthood, or consider themselves late bloomers.

Trying and struggling to find a niche or a place to fit — another common challenge among people with ADHD — also influences identity and sense of self. If people with BPD have incomplete or ever-changing keys, people with ADHD have complete keys, but they often struggle to find the right lock.

Individuals with BPD may talk of wanting to die or feeling a desire for death because they feel like they aren’t built for living in this world. They may say that they feel numb or not fully formed — feelings that fuel thoughts of suicide and lead to suicide attempts.

Self-harming behaviors are also common in BPD and are often associated with self-loathing and self-punishment. They may also be associated with efforts to relieve numbness and feelings of dissociation and depersonalization. Cutting, for example, produces pain and draws blood — all of which may affirm one’s existence.

Certainly, suicidality arises from many factors, regardless of condition. But in ADHD — and unlike in BPD — suicidal ideation often seem to arise from feeling like one does not know how to live, rather than wanting to die. My patients with ADHD who struggle with suicidal thoughts will say things like, “I don’t know how to ‘adult’” and, “I don’t know how to figure out life.” They’d have a zest for life, they say, if only their executive function demands were reduced, or if they were only able to find their niche.

Individuals with ADHD (especially teen girls) also face a greater risk for self-harming behaviors than do people without ADHD.^{4 5} Self-harming behaviors in ADHD are often tied to sensation seeking and dopamine release. (Not everything that is stimulating is necessarily pleasurable.) People with ADHD may also self-harm to relieve tension and ground themselves.

BPD is also highly comorbid with mood disorders, like depression and bipolar spectrum disorders.^{6 7} Bipolar disorders overlap so much with BPD that some researchers have introduced the idea of BPD being part of the bipolar spectrum.⁸

Extreme mood changes in BPD may arise from internal and external triggers, like an internal sense of agitation or problems in interpersonal relationships, respectively. Hypersensitivity and dichotomous thinking may distort perceptions and play a major role in intense reactivity.

Mood changes also tend to be more context-based in ADHD and in response to an external event, not so much to a sudden internal feeling.

(More on ADHD and emotional dysregulation in symptom #8 below.)

Since feelings of emptiness are modulated by level of stimulation, these feelings can quickly go away once the individual finds something that fulfills them in that moment, like getting in touch with a friend or engaging in their favorite hobby.

Anger in BPD isn’t always external. “Quiet BPD” has emerged as a term that describes, in part, BPD that is characterized by internalized anger, rage, and emotional episodes — in contrast to the outward emotional displays more commonly associated with this personality disorder.

It’s why individuals with ADHD may experience intense anger that is difficult to control. Even so, anger in ADHD is often a normal response to a stressor (which isn’t always the case with BPD); it’s the anger’s intensity that stands out in ADHD.

These episodes and symptoms tend to be transient, lasting minutes or hours, and occur most frequently in response to real or imagined abandonment. (See symptom #1.)

An individual with ADHD, for example, may be lost in thought, zoned out, or distracted to the point of appearing disconnected from the present moment. This is not the same as the experience of dissociation, which describes a disconnect from one’s body, thoughts, surroundings, and sense of reality. Even when an individual with ADHD appears disconnected, they are still connected and grounded internally or externally to something (likely a stimulating thought). Whether someone with ADHD becomes disengaged from the present often depends on how stimulated they are. Dissociative symptoms in BPD, on the other hand, are not modulated by stimulation, but by stress.