The purpose of this study is to explore the tolerability and effectiveness of transcranial direct current stimulation (tDCS) as a potential treatment for non-suicidal self-injury (NSSI). Individuals who engage in frequent NSSI will be randomized to 12 administrations of an active vs. inactive form of tDCS, paired with an Attention Training Technique task, over a two-week period. Functional MRI may be performed before and after this two week period. NSSI urges and behaviors will be monitored before, during, and after the period of tDCS administrations.

The purpose of this study is to explore the tolerability and effectiveness of transcranial direct current stimulation (tDCS) as a potential treatment for non-suicidal self-injury (NSSI). NSSI is the deliberate attempt to harm oneself, most often through cutting or burning, without suicidal intent. NSSI is a maladaptive emotion-regulation strategy often triggered by negative emotions, especially those involving feelings of rejection. tDCS is a low-cost, portable, well-tolerated, non-invasive form of brain stimulation that delivers a low current to a specific area of the brain via electrodes. Several studies have demonstrated its effectiveness in treating an array of conditions, depending on electrode placement, including depression and chronic pain. tDCS may also facilitate adaptive emotion regulation; researchers have also successfully used tDCS to reduce negative emotions and aggressive responses to social rejection. The investigators therefore seek to explore tDCS as a potential treatment for NSSI. This pilot feasibility study seeks 1) to examine how tDCS is tolerated in a sample of individuals who engage in frequent NSSI; 2) to gather pilot data regarding changes in emotional and neural responses during a social task after a series of tDCS sessions in this clinical population of individuals who engage in NSSI; 3) to gather pilot data on the effects of tDCS on NSSI behaviors and urges. The investigators seek to recruit a sample of 22 individuals who engage in frequent NSSI to complete all study procedures. Individuals will be randomized to receive active- or sham-tDCS for two twenty-minute applications on each of six alternating sessions over approximately two weeks for a total of 12 tDCS administrations, each paired with an Attention Training Task. Functional MRI (fMRI) may be performed at baseline and again after the completion of 12 applications of tDCS. Subjects' NSSI and urges to engage in NSSI will be recorded for four weeks in real-time, using an iPod- based system that reminds subjects to stop at certain times during the day to record their thoughts, feelings, and behaviors. This will allow measurement of NSSI urges and behaviors for one week before, two weeks during, and one week after the tDCS intervention. The long-term goal of this study is to identify a novel form of treatment for NSSI and to better understand NSSI pathophysiology.

Inclusion Criteria:

1. Age 18-60
2. Frequent current NSSI (including cutting in which the skin is broken; self-hitting in which there is bruising; or burning in which there is evidence of a burn. Will not enroll if skin-picking or scratching is the only form of self-injury): has engaged in ≥2 episodes of NSSI in the two months prior to enrollment
3. Capacity to provide informed consent
4. If carries a diagnosis of bipolar I or II disorder, taking or willing to begin a therapeutic dose of a mood stabilizer.
5. Normal hearing.
6. Physical capacity (e.g., manual dexterity) to set-up and self-administer tDCS. -

Exclusion Criteria:

1. Unstable medical conditions based on medical history or physical examination

2. Current psychotic disorder, mania, hypomania, intellectual disability

3. Dermatologic condition resulting in non-intact skin on the scalp

4. Significant suicidal ideation with a plan and intent that cannot be managed safely as an outpatient

5. Pregnancy, currently lactating, or planning to conceive during the course of study participation.

6. A neurological disease or prior head trauma with evidence of cognitive impairment. Subjects who endorse a history of prior head trauma and score ≥ 1.5 standard deviations below the mean on the Trailmaking A&B will be excluded from study participation.

7. Current alcohol or substance use disorder that is severe according to DSM-V criteria

8. Individuals who initiated or increased the dose of concurrent psychiatric medications (including antidepressants, anxiolytics, antipsychotic medications, mood stabilizers, and benzodiazepines) within two weeks prior to enrollment

9. Individuals who initiated psychotherapy within two weeks prior to enrollment

10. Current seizure disorder.

11. Use of anticonvulsant medications that target the GABA system (e.g., gabapentin).

12. Individuals currently using benzodiazepines who are unwilling or unable to refrain from the use of benzodiazepine medications for at least 72 hours before the first tDCS session and throughout the duration of the 2-week tDCS intervention.

13. Metal implants or paramagnetic objects contained within the body (including heart pacemaker, shrapnel, or surgical prostheses) which may present a risk to the subject or interfere with the MRI scan, according to the guidelines set forth in the following reference book commonly used by neuroradiologists: "Guide to MR procedures and metallic objects," F.G. Shellock, Lippincott Williams and Wilkins NY 2001. Additionally transdermal patches will be removed during the MR study at the discretion of the investigator.

14. Claustrophobia significant enough to interfere with MRI scanning

15. Weight that exceeds 325 lbs or inability to fit into MRI scanner

16. Suicide attempt within the past 3 months

17. Serious self-harm resulting in hospitalization within the past 3 months.

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Scan results, questionnaire answers, and data collected during the task may be used in future studies, and if shared with other investigators, information that identifies the scan, questionnaire responses, or task data with you will be removed before hand.

upon request

upon request

tDCS device programmed with codes to deliver active vs. sham tDCS in a blinded manner. Individual independent of study team managed randomization and provided codes for blinded tDCS administration.