Headings reflect the progression of logic in an article and thereby guide the reader. Headings also help break up the copy, making the article more attractive and easier to read.

If not present, copyeditors may suggest the addition of subheadings underneath the Introduction, Methods, Results, and Discussion sections during copyediting. 

Headings by Paper Type

Most papers have an Introduction, Methods, Results, and Discussion heading, followed by multiple subheadings. These papers include:

• Original Papers
• Reviews
• Tutorials
• Protocols
• Proposals

Other types of papers (eg, Viewpoint) with content that cannot follow those headings may have different headings and subheadings.

Research Protocols and Proposals

Headings for research protocols and proposals are often more flexible, but if possible, introduce the standard headings (Introduction, Methods, Results, Discussion).

For these papers, ensure the subheading "Ethics Approval" or similar is added to the Methods section, not Results. 

The Results section is often missing, because protocols and proposals typically do not report results. In this case, add a Results heading (H2 level), and ask the author to add 1-2 sentences about the current funding status, enrolment status, or expected results. For example, "The project was funded in ### and enrolment was completed XXX. Data analysis is currently underway and the first results are expected to be submitted for publication in YYYY." 

See also: What should I put into the results section of a protocol or proposal?

Similarly, the abstract should be reformatted to have the usual "Background - Objectives - Methods - Results - Conclusions" structure, with a similar sentence for results (when and what to be expected) and conclusions (what will be the significance of the findings).

Heading Styles

All headings must have a style label called Heading 1 (H1), Heading 2 (H2), Heading 3 (H3), and so on. You can use up to H5 (a subheading greater than H5 cannot be distinguished stylistically in the typeset PDF). The actual style of the heading (eg, font, bolding, italicization) does not matter as long as you select the correct label. Note that this is essential for our XML tagging scripts.

You must format the headings accordingly:

Heading 2 (H2)

• Introduction
• Methods
• Results
• Discussion
• References

Heading 3 (H3)

• Acknowledgments
• Authors’ Contributions
• Conflicts of Interest
• Abbreviations
• First-level subheadings (directly beneath the Introduction, Methods, Results, and Discussion)

Headings 4 and 5

• Successive subheadings within a section

Example

General Rules

• Headings (including subheadings) should be in title case.
  
• If an abbreviation has been introduced earlier, it may be used in/as a heading. Do not introduce abbreviations for the first time in a heading. Spell the term out in the heading if that is its first appearance and introduce the abbreviation, if appropriate, at the next appearance of the term.
• In general, avoid use of a single abbreviation or acronym as a heading; in such cases, add a qualifier or descriptor for clarity (eg, MRI technique or PCR analysis).
• There is no requisite number of subheadings. However, because headings are meant to divide a primary part into secondary parts, there should be a minimum of 2 subheadings per primary section if a subheading is used. If there is only one subheading, add a second subheading or delete the single subheading.  
  
• If subheadings are used, all text in the section must be included under a subsection. A subheading (for example, H3 level) needs to directly follow a primary heading (H2 level). This rule applies to all subheadings (H3, H4, etc) under the primary (H2 level) headings in a paper. The only exception is if there is a short introductory paragraph (eg, 1-2 sentences) after a primary heading; in this case, no subheading is needed to introduce this short paragraph.
• Often, Discussion sections will only have the subheading "Conclusions.” However, the first section of the Discussion also requires a subheading to meet the minimum requirement of 2-same level subheading within a section. Common subheadings include "Principal Findings," "Limitations," "Future Work," and "Conclusions". Make the authors aware of these additional subheadings during the first copyediting stage so that they can change the details of the subheadings if desired (see below for example).
• Avoid citing figures, tables, or references in a heading. Cite them appropriately in the text.
• Avoid soft line breaks (shift+enter) or extra line breaks (enter) between subheadings and paragraphs. This may lead to problems during XML script conversion.
• Avoid highlighting or italicizing words in paragraphs in lieu of proper formatting (see below for example).

Example: Correct. The length of the sentence under Methods is acceptable and doesn't require a subheading above it.

Example: Wrong. The length of the paragraph under Discussion is too long to not be under a subheading.

Example: The italicized list should instead be subheadings.