Trauma & Anxiety Therapy, NY.

Licensed Clinical Psychologist In Suffolk & Nassau County

Therapy For Anxiety, Depression, Trauma, Stress, In-Person & Online Telehealth Appointments

Dealing with Anxiety, Depression, or past Trauma? You're not alone.

Personalized therapy to help you heal and grow.
Call Now:  631-804-6937

Take the First Step Today

Ready to talk?
Call 631-804-6937 to get started.

Get to Know Dr. Nissen

Learn more about Dr. Nissen’s background, approach, and credentials.

Integration of

Clinical practice, scientific research, teaching, and professional leadership.
Nissen Psychology provides professional therapy services for anxiety, depression, and emotional healing”

Welcome to
Nissen Psychology PC

Struggling with Anxiety, Depression, or Trauma? You're Not Alone.

Whether you’re navigating overwhelming stress, struggling with anxiety or depression, or simply feeling disconnected from yourself or others—know that you're not alone. At Nissen Psychology PC, we believe therapy is more than just a space for crisis; it’s a space for understanding, healing, and transformation.
Our practice is built on warmth, trust, and collaboration. We take the time to truly understand your story—past and present—and tailor your therapy experience around what matters most to you. You’ll find a compassionate partner in your growth journey who listens without judgment, supports with empathy, and challenges with care.

Meet Dr. Nissen

Licensed Clinical Psychologist | Trauma Expert | Assistant Professor
Kevin J. Nissen, Ph.D., is a licensed clinical psychologist with experience treating trauma, anxiety, depression, and relationship issues. With advanced training in psychodynamic psychotherapy and years of experience working with veterans, first responders, and adults, he brings empathy, expertise, and insight to the therapy process. Dr. Nissen also serves as an Assistant Professor at Hofstra University’s School of Medicine and was the 2025 President of the NYSPA’s Psychoanalysis Division.
Read full Bio
Dr. Nissen, licensed psychologist at Nissen Psychology, providing expert therapy for anxiety, depression, and trauma

Our Approach to Therapy

01

Depth Over Surface

We go beyond just symptom management. By exploring your unconscious thoughts and past experiences, we uncover root causes—not just surface behaviors.

02

Break Old Patterns

Many struggles come from repeating the same emotional cycles. Therapy helps you recognize these patterns and create space for real change.

03

Growth That Lasts

Therapy isn’t just about feeling better—it’s about becoming stronger, more self-aware, and better equipped for the future.

Therapy Services

Supporting you through anxiety, depression, trauma, and more.

Trauma Therapy

Anxiety Therapy

Depression Therapy

Relationship Issues

Testimonials

Recognized by peers for empathy, professionalism, and lasting impact
  • “I can personally attest to Dr. Nissen's wide ranging expertise, direct yet gentle, humorous approach to treatment. He is a consistent, reliable, and deeply empathic clinician and I highly recommend him without hesitation.”

    — Dr. Mathew Brigante

  • "Dr. Nissen brings a rare depth of understanding to his work. He has a way of helping people feel seen and understood, while also guiding them toward meaningful insight and emotional growth. His presence is steady, thoughtful, and attuned. I highly recommend him to anyone seeking a therapist who can help create lasting, transformative change."

    — Dr. Logan Tuminelli

Reaching out for therapy is a brave step.
If you're ready to start your journey, we're here to help.

Call: 631-804-6937

Available Hours

We offer in-person appointments at our office in Stony Brook, NY as well as virtual options. Evening and weekend appointments available.

Phone

631-804-6937

Address

2500 Nesconset Hwy, Bldg 5D 
Stony Brook, NY 11790

Disclaimer

The information provided on this website is intended for general informational and educational purposes only and is not a substitute for professional psychological advice, diagnosis, or treatment. Viewing this website, using the information contained herein, or communicating with the practice through email or website contact forms does not establish a psychologist–patient relationship.

The services described on this website are intended for adults age 18 and older. This website is not directed toward minors and does not knowingly collect personal information from individuals under the age of 18.

This website does not collect, store, or transmit Protected Health Information (PHI) for advertising or marketing purposes. Some third-party services used for website analytics or advertising may receive anonymized website activity data, such as pages visited or general interaction with the site. This data is not linked to personal health information, patient records, or identifiable medical information.

If you are experiencing a mental health emergency, do not use this website to seek immediate assistance. Instead, call 911, go to your nearest emergency room, or contact the National Suicide & Crisis Lifeline at 988 for immediate support.

Psychological services are provided only in jurisdictions where the psychologist is appropriately licensed to practice.

While reasonable efforts are made to protect your privacy, electronic communications such as email or website contact forms may not be fully secure. You should avoid transmitting sensitive or confidential health information through these methods.

The website owner makes no warranties or representations regarding the accuracy, completeness, reliability, or suitability of the information contained on this website. Use of this website and reliance on any information provided herein is at your own risk.
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