Nexus Letter for Depression

June 21, 2024 – A nexus letter for depression is—or should be—an expert witness opinion based on comprehensive psychological or psychiatric evaluation findings.

I explain below why nexus letters for depression require an evidence-based psychological exam.

On this page ...

Dr. Worthen provides Independent Psychological Exams & Consultation to Attorneys

► Employment Law (ADA, sexual harassment)

► Civil Competencies (guardianship, testamentary capacity)

► Psychological injury (tort actions, insurance)

► Veterans disability claims (specializing in complex cases)

Click here for more information ...

Key Points

  1. For maximum credibility and persuasive power, psychologists should compose a nexus letter for depression predicated upon a comprehensive, evidence-based, and independent psychological exam.

  2. Treating doctors or therapists can write helpful nexus letters for depression, while avoiding dual-role conflicts. (I explain how below.)

  3. Psychologists who write nexus letters based on a record review alone risk ethics code violations.

  4. The connection (nexus) between a current depressive disorder and military service can  manifest in four ways: 
    (i) incurred during service;
    (ii) aggravated by military service;
    (ii) secondary to a service-connected medical condition;
    (iv) aggravated by a service-connected medical condition.

  5. Secondary service-connection claims seem simple, e.g., "the veteran has bad tinnitus and he subsequently became depressed, therefore the depression is secondary to the service-connected tinnitus." But psychologists should bear in mind that a temporal relationship is a necessary, but not sufficient, explanation for a cause-effect relationship. 

↑ Back to Top ↑

What Constitutes a Nexus Letter for Depression?

A nexus letter for depression can take many forms, some legitimate, some not. Let's start with a letter written by your treating healthcare professional.

Letter Written by Your Doctor or Therapist

Some mental health professionals (psychiatrists, psychologists, clinical social workers, professional counselors, etc.) will write a nexus letter for their patients or clients

A nexus letter for depression from a treating doctor or therapist, if written correctly, can provide substantial support for a veteran's claim.

Even though treating clinicians should not write nexus opinions,1 they can provide trustworthy descriptions of psychopathology, including symptoms, diagnosis, and functional impairment.

Such letters may have as much credibility as a good IPE (independent psychological exam).

Treating clinicians, e.g., mental health professionals one sees for medication, counseling, or psychotherapy, should avoid two potential problems:

  1. Dual roles with their patients or clients that create a potential conflict between their therapeutic obligations and the truth-finding responsibilities of experts who provide independent opinions.

    For example, stating that a veteran's major depression is "proximately due to or the result of"2 a service-connected medical condition is, in the eyes of the federal courts, an expert witness opinion.3

  2. Providing an nexus opinion without a full understanding of the legal requirements, ethical considerations, and professional standards.

↑ Back to Top ↑

This Is the Way: Nexus Letters Written by Treating Psychologists

Here is the right way for a psychologist to write a letter on behalf of their patient or client. I wrote this section as if I am talking to a psychologist. 

Write a letter summarizing your assessment, diagnosis, and course of treatment to date. Also discuss in detail your patient's mental disorder(s) have impaired their social and occupational functioning.  

Do not give expert witness opinions like this: "It is a least as likely as not that Mr. Patient's major depressive disorder is proximately due to or the result of diabetes-related complications and chronic pain, both service-connected medical conditions."

Instead, write a good clinical summary. For example:

Mr. Patient often expresses discouragement, a loss of hope, and feelings of despair related to his deteriorating functioning, especially after doctors amputated his left foot (due to a diabetes-related condition) and he started experiencing excruciating phantom limb pain several times a week.

Your veteran-patient might tell you that the nexus letter must say that it is at least as likely as not that his service-connected [medical condition] caused his depression.

Independent examiners' reports should contain such wording, but not a statement from a treating psychologist because you are not an independent evaluator.

As a treating psychologist you prioritize helping your patient above all else. You serve your patient's interests.

On the other hand, an independent examiner serves the truth. And sometimes the truth is not therapeutic, especially coming from a therapist who is supposed to be on the patient's side. 

As I state elsewhere on this site, if I am retained to conduct an IPE, I tell the veteran: "I perform objective, unbiased exams. I am not on your side. I am not on VA's side. I am an independent examiner."

But when a veteran sees me for psychotherapy, I would say simply, "I am on your side."

Many people understandably find this distinction—between treating psychologist and independent evaluator—difficult to grasp. I prepared a chart comparing clinical vs. forensic psychological (or psychiatric) assessment that might help.

For an in-depth understanding, see Recommended Reading List: Dual Role Conflicts, below.

↑ Back to Top ↑

Reliable Principles & Methods

Although the Federal Rules of Evidence (FRE) do not necessarily guide VBA staff's claim decisions, the Court of Appeals for Veterans Claims indicated that  FRE 702 in particular describes "important, guiding factors to be used by the Board [of Veterans Appeals] in evaluating the probative value of medical opinion evidence."

Rule 702 - Testimony by Expert Witnesses

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the proponent demonstrates to the court that it is more likely than not that:

(a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue;

(b) the testimony is based on sufficient facts or data;

(c) the testimony is the product of reliable principles and methods; and

(d) the expert's opinion reflects a reliable application of the principles and methods to the facts of the case.

Thus, a nexus letter for depression (or any other disability) should satisfy those criteria. 

↑ Back to Top ↑

Ethical Principles & Forensic Specialty Guidelines

If you read and seriously consider the implications of the APA ethical standards and forensic specialty guidelines reproduced below, you will see why a nexus letter for depression should be based on a comprehensive psychological evaluation. 

If a psychologist writes a nexus letter based on a record review alone, they should "make clear the impact of such limitations on the reliability and validity" of their opinion (forensic psychology specialty guideline 9.03).

APA Ethics Code (Psychologists)

The following APA ethical standards will sound familiar after just reading Rule 702.

Ethical Standard 2.01(f) When assuming forensic roles, psychologists are or become reasonably familiar with the judicial or administrative rules governing their roles.

Ethical Standard 2.04 Bases for Scientific and Professional Judgments: Psychologists' work is based upon established scientific and professional knowledge of the discipline.

Ethical Standard 9.01(a) Bases for Assessments: Psychologists base the opinions contained in their recommendations, reports, and diagnostic or evaluative statements, including forensic testimony, on information and techniques sufficient to substantiate their findings.

↑ Back to Top ↑

APA Specialty Guidelines for Forensic Psychology

The following Guidelines are presented in their entirety, except for 1.02, and citations to specific Ethics Code standards have been omitted. 

1.02 Impartiality and Fairness: When conducting forensic examinations, forensic practitioners strive to be unbiased and impartial, and avoid partisan presentation of unrepresentative, incomplete, or inaccurate evidence that might mislead finders of fact. This guideline does not preclude forceful presentation of the data and reasoning upon which a conclusion or professional product is based.

2.05 Knowledge of the Scientific Foundation for Opinions and Testimony: Forensic practitioners seek to provide opinions and testimony that are sufficiently based upon adequate scientific foundation, and reliable and valid principles and methods that have been applied appropriately to the facts of the case.

9.01 Use of Appropriate Methods: Forensic practitioners strive to utilize appropriate methods and procedures in their work. When performing examinations, treatment, consultation, educational activities or scholarly investigations, forensic practitioners seek to maintain integrity by examining the issue or problem at hand from all reasonable perspectives and seek information that will differentially test plausible rival hypotheses.

9.02 Use of Multiple Sources of Information: Forensic practitioners ordinarily avoid relying solely on one source of data, and corroborate important data whenever feasible (American Educational Research Association, American Psychological Association, & National Council on Measurement in Education, in press). When relying upon data that have not been corroborated, forensic practitioners seek to make known the uncorroborated status of the data, any associated strengths and limitations, and the reasons for relying upon the data.

9.03 Opinions Regarding Persons Not Examined: Forensic practitioners recognize their obligations to only provide written or oral evidence about the psychological characteristics of particular individuals when they have sufficient information or data to form an adequate foundation for those opinions or to substantiate their findings.

Forensic practitioners seek to make reasonable efforts to obtain such information or data, and they document their efforts to obtain it. When it is not possible or feasible to examine individuals about whom they are offering an opinion, forensic practitioners strive to make clear the impact of such limitations on the reliability and validity of their professional products, opinions, or testimony.

When conducting a record review or providing consultation or supervision that does not warrant an individual examination, forensic practitioners seek to identify the sources of information on which they are basing their opinions and recommendations, including any substantial limitations to their opinions and recommendations.

↑ Back to Top ↑


  1. In this article, I explain why healthcare professionals should not write medical opinions unless they have conducted a forensic mental health evaluation with the veteran. However, other healthcare clinicians, including psychologists, disagree.

    I encourage you to compare their reasoning with mine, and study the scholarly literature about the distinction between clinical and forensic psychology (and psychiatry).

    Also, each profession has its own ethics code and professional standards. Although psychology and psychiatry have very similar ethical principles with regard to this issue, I do not know as much about the ethics code or professional standards for nurse practitioners.

  2. 38 C.F.R. § 3.310 (“disability which is proximately due to or the result of a service-connected disease or injury shall be service connected”).

  3. Nieves-Rodriguez v. Peake, 22 Vet. App. 295, 304 (2008) (“both VA medical examiners and private physicians offering medical opinions in veterans benefits cases are nothing more or less than expert witnesses”).

↑ Back to Top ↑

Recommended Reading List: Dual Role Conflicts

The following articles elucidate issues involved in multiple role conflicts, and why treating clinicians should not write medical opinions in a nexus letter for depression.

Keep in mind that the following terms are synonymous: medical opinion, nexus opinion, expert witness opinion.

AMA Code of Medical Ethics (hereinafter AMA Ethics Code),

AMA Ethics Code, chap. 1, Patient-Physician Relationships, Opinion 1.2.6 – Work-Related & Independent Medical Examinations,

AMA Ethics Code, chap. 3, Privacy, Confidentiality & Medical Records, Opinion 3.2.3 – Industry-Employed Physicians & Independent Medical Examiners,

Stuart A. Anfang, Liza H. Gold & Donald J. Meyer, AAPL Practice Resource for the Forensic Evaluation of Psychiatric Disability, 46 J. Aᴍ. Aᴄᴀᴅ. Psʏᴄʜɪᴀᴛʀʏ L. S2 (2018),

Stuart A. Greenberg & Daniel W. Shuman, Irreconcilable Conflict between Therapeutic and Forensic Roles, 28 Pʀᴏ. Psʏᴄʜ. Rsᴄʜ. & Pʀᴀᴄ. 50 (1997),

Gᴀʀʏ B. Mᴇʟᴛᴏɴ ᴇᴛ ᴀʟ., Psʏᴄʜᴏʟᴏɢɪᴄᴀʟ Eᴠᴀʟᴜᴀᴛɪᴏɴs ғᴏʀ ᴛʜᴇ Cᴏᴜʀᴛs: A Hᴀɴᴅʙᴏᴏᴋ ғᴏʀ Mᴇɴᴛᴀʟ Hᴇᴀʟᴛʜ Pʀᴏғᴇssɪᴏɴᴀʟs ᴀɴᴅ Lᴀᴡʏᴇʀs 90–92 (4th ed., 2018).

Gérard Niveau, Tony Godet & Birgit Völlm, What Does Impartiality Mean in Medico-Legal Psychiatry? An International Survey, 66 Iɴᴛ'ʟ J. L. & Psʏᴄʜɪᴀᴛʀʏ 101505 (2019),

Paul M. Richards & Hal S. Wortzel, Avoiding Dual Agency in Clinical and Medicolegal Practice, 21 J. Psʏᴄʜɪᴀᴛʀɪᴄ Pʀᴀᴄ. 370 (2015),

Larry H. Strasburger, Thomas G. Gutheil, & Archie Brodsky, On Wearing Two Hats: Role Conflict in Serving as Both Psychotherapist and Expert Witness, 154 Aᴍ. J. Psʏᴄʜɪᴀᴛʀʏ 448,

↑ Back to Top ↑

You might like these articles ...

What Do You Think?

iconImage of the Google sign-in icon

I value your feedback!

If you would like to comment, ask questions, or offer suggestions about this page, please feel free to do so. Of course, keep it clean and courteous.

You can leave an anonymous comment if you wish–just type your first name.

If you want to receive an email when someone replies to your comment, click the icon on the lower right of the comment box to use Google Sign-in. (Your email remains private.) 

Important: Do not type your email address or other identifying information into your comment as it will appear on the Internet for everyone to see ... and for spam bots to harvest so that spammers can sell your email address to other spammers.

HTML Comment Box is loading comments...

How did you build this website?

I used Solo Build It! to build this website in 2004 and still use it today, especially for the extremely helpful business guidance and the superior search engine optimization.

Note: If you click on one of these links and you decide to purchase Solo Build It! I earn a small affiliate commission. Your cost is the same either way. If you do not want me to earn an affiliate commission, just google "solo build it".