This post is the first in a professional series (including personal experience) on the overlooked behaviours of individuals with Cluster B psychopathology.

The Hidden Danger of Stalking: A Red Flag for Cluster B Psychopathology

In my years as a clinical psychotherapist, I’ve sat across from countless clients whose lives have been upended by stalking. They come in shaken, second-guessing their own instincts, often blaming themselves for the relentless texts, the uninvited appearances, the suffocating sense of being watched. As a society, we’ve conditioned them to downplay it—to see it as flattery, obsession, or just “someone who can’t move on.” But in my office, and in the research I lean on daily, I see something else: stalking is often a glaring signal of Cluster B psychopathology, and we’re missing it at our peril.

Cluster B personality disorders—narcissistic, borderline, histrionic, and antisocial—aren’t rare curiosities. They show up in my practice more often than most people realize, and they share a troubling hallmark: a profound struggle with boundaries, self-regulation, and empathy. Stalking isn’t just a behavior these clients might exhibit; it’s a manifestation of the chaos beneath the surface. I’ve worked with individuals who stalk because rejection shatters their fragile sense of self, like a narcissist whose ex becomes a symbol of their wounded pride. I’ve seen others, perhaps wrestling with borderline traits, stalk out of a desperate need to cling to someone they fear losing forever. And then there are the antisocial cases—those who treat it like a chess game, reveling in the control it gives them over their target.

The numbers back this up. Research, like studies published in The Journal of Forensic Psychiatry & Psychology, shows a strong correlation between stalking and Cluster B traits. In the U.S. alone, the Department of Justice estimates that over 7 million people experience stalking in their lifetime. A significant chunk of those cases—more than we’re comfortable admitting—involve perpetrators whose behavior hints at something deeper than a bad breakup or unrequited love. And yet, I watch as courts, families, and even some clinicians shrug it off as “harassment” without peering into the why.

From where I sit, the ‘why’ matters. Stalking isn’t static—it escalates. I’ve had clients describe how it starts innocently enough: a flood of messages, a “chance” meeting at their favorite coffee shop. But for someone with Cluster B pathology, that’s not where it ends. Rejection doesn’t deter them; it ignites them. A 2017 study in Aggression and Violent Behavior found that stalkers with personality disorders are disproportionately likely to become violent when their pursuit is blocked. I’ve seen this play out—clients who’ve gone from annoyed to terrified as gifts turn into threats, and surveillance turns into confrontation, involvement with the Police, the courts and psychiatric intervention.

So why do we keep missing it? In part, because Cluster B disorders are masters of disguise. The charm of a narcissist, the emotional pull of a borderline plea, the calculated coolness of an antisocial mind—these traits muddy the waters. I’ve had clients tell me they hesitated to report their stalker because “he seemed so nice at first” or “she just needs help.” And they’re not wrong—help is needed. But as a therapist, I know that help doesn’t come from ignoring the signs. It comes from recognizing that stalking isn’t a standalone quirk; it’s a symptom of a mind that can’t process boundaries or loss in a healthy way, an overarching need for control and yes, a sadistic quality.

This isn’t about labeling every stalker as a textbook case—diagnosis is complex, and I don’t wield it lightly. But it’s about pattern recognition, something I’ve honed over years of practice. When I hear about someone who can’t let go, who reacts to “no” with rage or obsession, who sees another person as an extension of their own needs, I’m listening for Cluster B echoes. And I’m urging anyone reading this to listen, too. Because every time we dismiss stalking as “just drama,” we’re leaving victims vulnerable and letting a warning sign fade into the background.

In my practice as a clinical psychotherapist, I’ve seen stalking cases that leave you marveling at how cunningly they unfold. Clients come to me, exhausted and unnerved, describing not just one person shadowing their every move, but a network—friends, family, even strangers—unwittingly roped into the pursuit. When the stalker has a Cluster B personality disorder—narcissistic, borderline, histrionic, or antisocial—their ability to dodge consequences and weaponize others isn’t just luck. It’s a chilling byproduct of their pathology, and it’s something we need to understand if we’re ever going to stop it.

Cluster B individuals are often masters of perception. They don’t just stalk; they orchestrate. Take narcissism, for example. I’ve worked with clients whose ex-partners spun tales of betrayal so convincing that mutual friends became flying monkeys—psychology’s term for those manipulated into doing the dirty work. “She cheated on me,” he’ll say, tears in his eyes, “I just need to know she’s okay.” Suddenly, those friends are checking the victim’s social media, passing along updates, all under the guise of concern. The narcissist gets their fix—control, information, proximity—without lifting a finger. Or the anti-social who plays the victim to naive vulnerable people on social media, with the sole purpose of using them to engage in anti-social behaviours and harming others.

Borderline personality dynamics can look different but hit the same mark. I’ve seen cases where someone with BPD traits leans on their emotional intensity to pull others in. “I can’t live without him,” she’ll express and cry to a sibling or coworker, “just drive by his house so I know he’s safe.” That desperation flips a switch—people want to help, to soothe the pain they’re witnessing. They don’t realize they’re feeding an obsession, extending the stalker’s reach while keeping her hands clean. It’s not always malice (although sometimes it is) on the helpers’ part; it’s human nature exploited by a mind that thrives on chaos.

Then there’s the antisocial angle, which I find particularly insidious. These individuals don’t bother with manipulative ‘sob stories’—they calculate. I’ve had clients stalked by someone who’d charm a neighbor into reporting their comings and goings, maybe with a casual, “I’m planning a surprise for her birthday.” The neighbor, flattered to be included, complies. Or they’ll catfish online, posing as the victim’s friend to extract details from others, all while the victim wonders how their stalker always knows where they are. It’s cold, deliberate, and terrifyingly effective.

So how do they get away with it? For one, Cluster B traits are a perfect storm of charisma and manipulation. In session after session, I’ve seen how they blur lines. The narcissist’s grandiosity makes their entitlement feel justified—“I deserve to know what she’s doing.” The histrionic’s flair for drama turns their pursuit into a tragic romance others buy into. Antisocial types bank on people’s naivety, while borderline volatility can guilt-trip anyone into compliance. They’re not just stalking—they’re curating a narrative that keeps suspicion off them and accountability at bay.

Society helps them, too. Stalking laws are notoriously hard to enforce—restraining orders mean little without concrete proof, and “he said, she said” muddies the water. Add in bystanders who don’t want to “overreact” or who fall for the stalker’s spin, and you’ve got a recipe for impunity. I’ve had clients whose pleas for help were dismissed because the stalker “didn’t seem dangerous” or “just needs closure.” Meanwhile, the victim’s life unravels, and the helpers don’t even know they’re complicit. The Police and court system are not trained and often make these cases worse.

The scariest part? These individuals don’t see it as wrong. In their world, the end—reclaiming power, soothing abandonment fears, winning the game or competition—justifies every mean. I’ve sat with Cluster B clients who genuinely believe their target “owes” them, that their actions are righteous or that their behaviours are justified under the ‘guise’ of social justice. That disconnect lets them pull strings without hesitation, turning others into tools whilst they stay in the shadows.

Breaking this cycle starts with awareness. If someone’s asking you to “check up” on an ex, dig for details, or play messenger, pause. Ask why. Look at the pattern. And if you’re the one being stalked, know this: their ability to recruit others doesn’t make your fear less real—it makes their dysfunction more dangerous. In my office, I tell clients to trust their gut, document everything, and lean on support that doesn’t buy the stalker’s script.

I have also encountered a more disturbing subset of Cluster B individuals—most often those with narcissistic or borderline personality disorders—who target their therapists with stalking behaviors, a phenomenon that reveals the profound severity of their pathology. These clients, triggered by terminated sessions, enforced boundaries, disagreement, family court matters or the end of treatment, engage in relentless pursuits: incessant phone calls, uninvited appearances at my office, fake emails, fake inquiries, manipulating others to surveil my whereabouts and/or reputation smearing (via secret Facebook groups, fake Facebook pages, Facebook messenger groups, using other people to do their dirty work for them, etc). This is not a misguided expression of attachment; it is a calculated or desperate bid for control, a response to perceived rejection or an unwillingness to relinquish the therapist as an emotional anchor. Research underscores the seriousness of this pattern: The Journal of Forensic Psychiatry & Psychology reports that Cluster B traits, particularly borderline personality disorder (primary with a secondary personality disorder), are present in up to 45% of less forensically severe stalking cases, often fueled by abandonment fears or entitlement. A separate study found that 15% of individuals who stalked their psychiatrists exhibited BPD, marking therapists as vulnerable targets when we symbolize stability or threaten their dominance. In my practice, these incidents serve as a grave reminder of the unchecked emotional dysregulation and boundary violations inherent in their disorders, exposing a capacity for intrusion that demands vigilance and resolute response.

Tania has both professional and personal experience with Cluster B personalities who stalk other individuals. She is a government recognised ‘Victim of Crime’ of a serial vexatious litigant and stalker, and knows first hand the depths of chaos these individuals go to harm others. She regularly consults with both clients and therapists who are being stalked, harassed or mobbed. She is currently writing a book, including real life examples and forensic evidence, detailing how these disordered individuals operate in society.

If you need assistance, therapy, or consultations in this specific area, contact Tania at consulttaniamarshall@gmail.com

Purcell, R., Powell, M. B., & Mullen, P. E. (2005). Clients who stalk psychologists: Prevalence, methods, and motives. Professional Psychology: Research and Practice, 36(5), 537–543.

• This study surveyed 830 Australian psychologists, finding that 19.5% had been stalked by clients for two weeks or more. It notes that personality disorders, including Cluster B traits like resentment (linked to narcissistic or borderline features), were common among perpetrators, with therapists often targeted due to perceived rejection or infatuation.

Mullen, P. E., Pathé, M., Purcell, R., & Stuart, G. W. (1999). Study of stalkers. American Journal of Psychiatry, 156(8), 1244–1249.

• Examining 145 stalkers referred to a forensic psychiatry clinic, this study identified personality disorders as predominant among “rejected” stalkers (often ex-partners or professionals like therapists), with Cluster B traits such as borderline and narcissistic features noted in cases involving emotional dysregulation and entitlement directed at figures like therapists.

Krammer, A., Stepan, A., Baranyi, A., Kapfhammer, H. P., & Rothenhäusler, H. B. (2007). [The effects of stalking on psychiatrists, psychotherapists, and psychologists: Prevalence of stalking and its emotional impact]. Der Nervenarzt, 78(7), 809–817. (German)

• This German study found that 26.5% of surveyed mental health professionals had been stalked, with many perpetrators exhibiting psychotic or personality disorders, including Cluster B traits like borderline instability or narcissistic rage, often triggered by therapeutic boundaries.

Sandberg, D. A., McNiel, D. E., & Binder, R. L. (2002). Stalking, threatening, and harassing behavior by psychiatric patients toward clinicians. Journal of the American Academy of Psychiatry and the Law, 30(2), 221–229.

• This research identified that patients with personality disorders, particularly Cluster B (e.g., borderline and antisocial), were more likely to stalk or harass clinicians, often as a response to perceived abandonment or control issues within the therapeutic relationship.

Whyte, S., Penny, C., Christopherson, S., Reiss, D., & Petch, E. (2011). The stalking of psychiatrists. International Journal of Forensic Mental Health, 10(3), 254–260.

• Focused on psychiatrists in secure settings, this study found that Cluster B disorders, notably borderline and narcissistic personality disorders, were prevalent among patients who stalked their psychiatrists, with motives tied to rejection sensitivity or a need for dominance.

Meloy, J. R. (1998). The psychology of stalking: Clinical and forensic perspectives. San Diego, CA: Academic Press.

• In this seminal work, Meloy discusses stalking of clinicians, linking Cluster B traits—especially narcissistic entitlement and borderline instability—to cases where therapists become targets due to their role as authority figures or emotional supports, with specific chapters referencing forensic cases.