Table 1.

Epidemiological studies

Directionality of associations	Study’s author(s), year	Country	N at follow-up (retention rate), % females and mean (M) age at baseline	Follow-up period	Measure (s)	BPD measured at baseline; age of BPD assessment	Findings
NSSI predicting BPD	Nakar et al., 2016	Germany; 26 schools – The Saving and Empowering Young Lives in Europe study	N = 513 (36%); 62% females; Mage = 14.5 years	2 years (3 assessments)	DSH Inventory SCID-II (15-item BPD screener and interview)	No; Mage = 14.5 years at baseline + 2 years	Statistically significant differences on number of BPD criteria scores between low, moderate and high risk NSSI groups (F (2,510) = 1229.584, p < 0.001, η2 = 0.828), with a mean of 7.33 BPD criteria for the high-risk group NSSI (overall mean number of BPD criteria = 3.62).
NSSI and suicidal ideation predicting BPD	Scott et al., 2015	USA	N = 1950 (80%), includes 4 cohorts; all females; age at baseline = 5–8 years	6–9 years 1st SI measure at age 10 1st NSSI measure at age 13 both measures assessed until ages 16–19	CSI-4 ASI-4 ASRI-4 SCID-I IPDE-BOR (screening questionnaire)	No; Ages 16–19	Those who reported SI-only and SI + NSSI both had significantly more BPD symptoms than those with no SI or NSSI. And the SI + NSSI group reported significantly more BPD symptoms than the SI-only group. Observed range of BPD scores 0–8; No SI or NSSI M = 1.2, SD = 1.64; SI-only M = 2.22, SD = 1.99; SI + NSSI M = 2.84, SD = 2.05, (F (2,1947)= 70.30, p < .001).

Note. BPD borderline personality disorder, NSSI non-suicidal self-injury, SI suicidal ideation, DSH The Deliberate Self-Harm Inventory, SCID-II-PQ The Structured Clinical Interview for DSM-IV Axis II Personality Disorders, CSI-4 Child Symptom Inventory 4th-edition, ASI-4 Adolescent Symptom Inventory 4th-edition, ASRI-4 Adult Self-Report Inventory 4th-edition, SCID-I The Structured Clinical Interview for DSM-IV Axis I, IPDE-BOR The International Personality Disorder Examination-Borderline