Ernest Raba (defendant) appeals a judgment entered against him in the amount of $850,000 after a jury found that Michael Cobo (Cobo) was injured by defendant’s negligence.
Defendant is a psychiatrist practicing in the Durham, North Carolina area. Cobo began to see defendant as a patient when Cobo moved to Durham to accept a job at Duke Medical School. Cobo had previously been diagnosed and treated for depression during medical school and during his residency in Miami. During treatment for depression in Miami, Cobo had been treated with an antidepressant drug which produced adverse side effects. In late 1980 Cobo began a course of treatment with defendant who diagnosed Cobo as suffering from chronic depression. The treatment consisted of psychoanalysis four times a week which continued until December 1986, when Cobo tested positive for HIV.
*322Cobo told defendant that he did not wish to be treated with medication because his previous treatment with medication had “affected him badly” and had been unhelpful. Further, during the initial sessions defendant did not take notes pursuant to Cobo’s request. Cobo was worried about protecting his identity and keeping the treatment a secret.
During his time in psychoanalysis with defendant, Cobo’s depression became worse, which negatively affected his marriage, relationships with co-workers, and his job to the point that he was eventually removed from Duke’s tenure track. Beginning in 1982 or 1983, he increased his abuse of alcohol and his use of marijuana, which he had begun using before seeking treatment from defendant. In 1981 Cobo began having sex with males “on a monthly basis,” including sex with male prostitutes. Cobo had sex with other men before he began seeing defendant, but only infrequently. Defendant advised Cobo that he “was making some very dangerous choices [about sexual partners and homosexual activity] and recommended that they stop,” and talked to Cobo about the risk of sexually transmitted diseases.
After Cobo was diagnosed with HIV, defendant began to treat him in a more supportive manner, offering more practical feedback and suggestions on ways to deal with his HIV status, including getting medical care, his substance abuse and how to tell his wife. After being diagnosed with HIV, defendant prescribed a medication for Cobo to treat his anxiety as well as depression and continued to see defendant four times a week. In December 1988 the doctor-patient relationship between Cobo and defendant was terminated and Cobo began seeing another psychiatrist who prescribed an antidepressant medication. Once the medication took effect, Cobo’s depression improved.
Dr. John Monroe, Jr., an expert in the field of psychiatry, testified that “major depression,” from which Cobo was suffering, was a “biologic deregulation” that has to do with “chemical imbalances.”
Cobo and his wife Virginia Cobo (collectively plaintiffs) filed a complaint against defendant seeking damages and alleging misdiagnosis and negligent treatment. Plaintiffs’ complaint also alleged that “early on in the treatment” defendant “discouraged the use of any Medications” and “failed to prescribe appropriate medications,” continued to treat Cobo with psychotherapy when he knew or should have known that it was less effective than other methods, including prescribing medications, and defendant “failed to keep notes on his *323sessions with [Cobo] in order to follow the course and effect, or lack thereof, of his therapy.”
Defendant claimed as affirmative defenses that Cobo was con-tributorily negligent and that the claims for acts occurring prior to December 1986 were barred by the statute of limitations.
Defendant’s request that the trial court instruct the jury on contributory negligence was denied. Defendant also requested that the trial court instruct the jury on the statute of limitations, contending that all claims arising from conduct occurring before December 1986 were barred because after plaintiff was diagnosed as HIV positive, defendant’s treatment of plaintiff was “completely different.” The trial court denied this request as well. The trial court submitted a single issue of negligence to the jury (“Was the plaintiff... injured by the negligence of the defendant”) and instructed them to answer the issue “yes” if they determined that Cobo had met his burden of proving either negligent diagnosis or negligent treatment.
The issues are whether (I) an instruction on contributory negligence should have been submitted to the jury; and (II) all claims relating to conduct occurring before December 1986 are barred by the statute of limitations.
I
[1] The trial court must instruct the jury on a claim or defense if there is substantial evidence, when viewed in the light most favorable to the proponent, of the claim or defense. Dixon v. Taylor, 111 N.C. App. 97, 103, 431 S.E.2d 778, 781 (1993); see Holtman v. Reese, 119 N.C. App. 747, 750, 460 S.E.2d 338, 341 (1995). Substantial evidence is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion. State v. Wheeler, 122 N.C. App. 653, 656, 471 S.E.2d 636, 638 (1996).
Contributory negligence is “negligence on the part of the plaintiff which joins, simultaneously or successively, with the negligence of the defendant ... to produce the injury of which the plaintiff complains.” Watson v. Storie, 60 N.C. App. 736, 738, 300 S.E.2d 55, 57 (1983).
[T]o . . . constitute contributory negligence in a medical malpractice action, a patient’s negligence must have been an active and efficient contributing cause of the injury, must have cooperated with the negligence of the malpractitioner, must have entered *324into proximate causation of the injury, and must have been an element in the transaction on which the malpractice is based.
Jensen v. Archbishop Bergan Mercy Hosp., 459 N.W.2d 178, 186 (Neb. 1990); see David M. Harney, Medical Malpractice § 24.1, at 563-64 (3d ed. 1993) (hereinafter Harney). Failure to follow a physician’s instructions may also give rise to contributory negligence. McGill v. French, 333 N.C. 209, 220-21, 424 S.E.2d 108, 114-15 (1993); see Harney § 24.1(A), at 564-65. When a patient’s negligent conduct occurs subsequent to the physician’s negligent treatment instead of concurrently or simultaneously, recovery by the patient should be mitigated and not completely defeated pursuant to a contributory negligence theory. Harney § 24.5, at 571; Miller v. Miller, 273 N.C. 228, 239, 160 S.E.2d 65, 74 (1968) (contrasting contributory negligence with the “doctrine of avoidable consequences”). Expert testimony is not necessary to establish proximate cause when the jury, using its “common knowledge and experience, is able to understand and judge the action of [plaintiff].” McGill, 333 N.C. at 218, 424 S.E.2d at 113 (quoting Powell v. Shull, 58 N.C. App. 68, 71, 293 S.E.2d 259, 261, disc. rev. denied, 306 N.C. 743, 295 S.E.2d 479 (1982)).
Contributory negligence as a defense is inapplicable “where a patient’s conduct provides the occasion for care or treatment that, later, is the subject of a malpractice claim, or where the patient’s conduct contributes to an illness or condition for which the patient seeks the care or treatment on which a subsequent medical malpractice [claim] is based.” Harney § 24.1, at 564. In other words, a person’s use of alcohol cannot constitute contributory negligence in a malpractice action against a physician treating him for alcohol abuse. See Cowan v. Doering, 522 A.2d 444, 450 (N.J. Super. 1987) (patient under physician’s care for taking an overdose of sleeping pills who jumped out of window and brought malpractice action against physician for failure to take precautionary steps to prevent her attempt at suicide was not contributorily negligent because the suicidal conduct was the very symptom for which patient was being treated), aff’d, 545 A.2d 159 (N.J. 1988). On the other hand, a person’s use of alcohol could constitute contributory negligence in a malpractice action against a physician treating that person for a broken back, provided the use of alcohol simultaneously joined with the physician’s negligence in contributing to the injuries.
In this case Cobo sought care and treatment for his depression. On the face of this record there is evidence that a reasonable mind *325might accept as adequate to support the conclusion that Cobo’s sexual activities with other men did not contribute to the depression for which he sought treatment from defendant. Although there is evidence that Cobo was having intermittent sex with other men prior to his treatment by the defendant, there is no evidence that his sexual activities (prior to or during his treatment by the defendant) was the cause of his depression. Indeed, there is evidence that Cobo’s depression was the result of a biological condition. Accordingly, because there is substantial evidence that Cobo’s conduct during the time he was being treated by the defendant joined simultaneously with the negligent treatment1 of the defendant to cause Cobo’s injuries, the trial court erred in not submitting the issue of contributory negligence to the jury on this basis.2
There are also other grounds that support submission of the issue of contributory negligence. Defendant produced substantial evidence that he was hindered in his diagnosis and treatment due to several conditions Cobo imposed on him. Cobo initially refused to pursue a course of treatment involving medication due to the effects that a previous medication had upon him. Further, to ensure that his confidentiality was protected, Cobo requested that defendant take no notes during the sessions. Thus there is substantial evidence that these actions by Cobo occurred simultaneously with defendant’s negligent treatment and diagnosis to cause Cobo’s injuries.
II
[2] Defendant contends that the three year statute of limitations is a bar to any action arising out of treatment rendered before December 1986. Defendant argues that the treatment rendered after December 1986 was distinctly different from that rendered before *326December 1986, and therefore the continuing course of treatment doctrine is inapplicable.
Section l-15(c) provides that a cause of action for malpractice accrues “at the time of the occurrence of the last act of the defendant giving rise to the cause of action.” N.C.G.S. § l-15(c) (1996). Pursuant to section l-15(c), a cause of action for malpractice has a statute of limitations of three years. Pursuant to the continued course of treatment doctrine, however, a cause of action does not accrue until the conclusion of the physician’s treatment of the patient, so long as the patient has remained under the continuous treatment of the physician for the injuries which gave rise to the cause of action. Stallings v. Gunter, 99 N.C. App. 710, 714, 394 S.E.2d 212, 215, disc. rev. denied, 327 N.C. 638, 399 S.E.2d 125 (1990). It is not necessary that the treatment rendered subsequent to the negligent act be negligent if the physician continued to treat the patient for the disease or condition created by the original act of negligence. Id. at 714-15, 394 S.E.2d at 215.
At the same time that Cobo tested positive for HIV, defendant began a “more supportive” form of analysis and prescribed medication for Cobo’s anxiety. Cobo’s treatment, however, did not change in that Cobo continued to meet with defendant four times a week to discuss his problems and to learn how to control and manage those problems, although after 1986 the sessions primarily dealt with Cobo’s HIV status. We determine that despite any change in treatment, because defendant continued to treat Cobo after 1986 for conditions that Cobo has alleged were caused by defendant’s negligence before 1986, the continuing course of treatment doctrine is applicable and plaintiffs’ action was timely filed.
We have addressed and reject without discussion the defendant’s argument that the trial court erred in denying his motions for directed verdict and post trial motions. Because we are ordering a new trial, it is not necessary to address the other issues raised on appeal.
New trial.
Judge MARTIN, Mark D., concurs.
Judge McGEE dissents in part and concurs in part.