In APA Style, semicolons are used in several ways:

• to join independent clauses that are closely related,
• to separate series of items if the items themselves contain internal commas, and
• to separate multiple citations that are enclosed by a single pair of parentheses.
• to join adjacent parenthetical citations
• to separate items in vertical lists

Joining Independent Clauses

Semicolons can be used to join independent clauses in two situations:

Independent clauses not joined by a conjunction

Use a semicolon to separate two independent clauses that are not joined by a coordination conjunction (i.e., and, but, or, nor, for, yet, or so) if the clauses are closely related.

Example:

Mean jail testing density for females screened at Clinic S was 54.5 tests/1,000 population/year; in comparison, testing for females at Clinic O was 7.9 tests/1,000 (p < 0.001).

The Richmond Agitation and Sedation Scale was used to monitor sedation; the Confusion Assessment Method for the ICU was used to assess delirium.

Driving forces initiate change; restraining forces oppose change (Lewin, 1951).

Independent clauses with transitional phrases and conjunctive adverbs

A semicolon can join two independent clauses in which the second clause begins with a transitional phrase or a conjunctive adverb. Examples of such conjunctive adverbs are

Examples:

Obesity was not associated with low health literacy in this study; however, this lack of association could have been due to sample demographics.

Inter-rater reliability was not evaluated for consistency; moreover, no tests were performed to analyze internal consistency.

These results indicate that the intervention improved the outcomes; for example, improvements were seen in the follow-up assessment.

More than 85% of ICU physiologic alarm events are technically false or occur because of manipulation by clinicians; in other words, fewer than 15% of alarm events are clinically relevant.

These procedures are not curative; rather, they result in altered hemodynamics (Pike, 2007).

A Series of Items with Internal Commas

In a series of items wherein the items themselves contain one or more internal commas, use a semicolon to separate the items.

Examples:

Relevant demographics were age, M = 51.3 years, 98% Cl [27.3, 35.2]; years of education, M = 7.4 [7.2, 11.3]; and weekly income, M = 897 [641, 902].

The patient population is racially heterogeneous (i.e., White, 52%; Hispanic, 37%; Asian, 23%; Black, 3%; Native American, 0.2%; and “other,” 27%).

The OR pilot team briefing and debriefing entailed conducting pre- and post-intervention; education for nurses, physicians, and technicians; and provision of educational materials to other clinical staff members.

The parameters include (a) the extent to which nurses’ jobs and the community in which the nurses live are similar to, or fit with, other aspects of their life; (b) the extent to which the nurses have links to other people and activities; and (c) the ease with which the links can be broken.

Parenthetical expressions that contains citations of two or more sources

In a parenthetical expression that contains citations of two or more sources, separate the sources with a semicolon.

Example:

The care that patients receive is not always consistent with their preferences (Connors, 1995; Heyland et al., 2013; Mack et al., 2010).

Occupational injury is a significant workforce and public health concern (Centers for Disease Control and Prevention [CDC], 2010a, 2010b; Davis, Castillo, & Wegman, 2000; Levy & Wegman, 2000).

Palliative care decreases readmissions and reduces symptom burden in patients with various medical conditions (Brumley, Enguidanos & Cherin, 2003; Rabow et al., 2013).

Adjacent Parenthetical Expressions

APA Style does not permit “back-to-back” parentheses. Instead, use a semicolon to join two or more adjacent parenthetical expressions.

In the following example, we join two parenthetical expressions to form a single parenthetical expression:

Rewrite

“(12.4%) (ISHLT, 2016; Salva et al., 2014)”   as   “(12.4%; ISHLT, 2016; Salva et al., 2014).”

Correct version of the sentence:

Adolescents comprise nearly 33% of these transplants but have the lowest median survival rate of all age groups (12.4%; Salva et al., 2014).

Examples:

These disabilities include deficits in functional areas (e.g., deficits in attention span; Schmidt et al., 2009b).

The readmission rate of the non-PC cohort was still found to be higher than that of the PC cohort (63.2% vs 29.0%, respectively; p < .01)

Note regarding semicolons with parentheses and brackets:

When a statement’s context requires a semicolon at the end of an expression that is enclosed in parentheses or brackets, the semicolon follows the closing parenthesis or bracket:

The participant said she had “this disease” [HIV/AIDS]; she had one child at home.

Vertical List Punctuated as a Sentence

In a numbered vertical list that (a) completes a sentence begun in an introductory element and (b) consists of phrases or sentences with internal punctuation, semicolons may be used between the items, and a period should follow the final item.

Example:

Among the report’s guidelines, four pertain to patient autonomy:

• The choice to forego resuscitation should be made by a competent, informed patient;
• Making medically and morally appropriate treatment decisions does not mean that legal statutes pertaining to  wrongful death or homicide require changing;
• The primary responsibility for ensuring a morally sound process . . . .

Semicolons with Other Punctuation

Closing quotation marks

Semicolons follow closing quotation marks:

Participant 32 said that she knew smoke is “unhealthy”; most of the other participants voiced similar opinions.

References

American Psychological Association.  (2009). Publication Manual of the American Psychological Association, Sixth Edition. (pp. 89-90).  Washington, DC: American Psychological Association.

University of Chicago. (2003). “Semicolon,” in Chicago Manual of Style, 15th Edition; p. 256.