Is Suicidal ideation a synonym of Suicidal thoughts

It's unfortunate that there wasn't a reason specified for removing it before.  I think people typically view suicidal thoughts and suicidal ideation as comparable although I guess it's conceivable that suicidal ideation might be viewed as broader term.  Often one is making an inference about whether suicidal ideation is present based on patient's statements when asked directly.  But ideation might also be inferred from other observations such as making a statement on social media or making vague references (e.g., "You'll be sorry when I'm not around any more." ) 

Paul, Laura -

I just did a quick search of papers indexed in PubMed (n=18, so not many) with  "suicidal ideation" in the title. I also looked at a couple of instruments used to measure suicidal ideation. 

Some papers use the term and never define what they mean by suicidal ideation (no narrative definition OR operational definition provided). One author defined suicidal ideation simply as "thoughts of suicide". Other authors define it as a specific type of thought process (preoccupied, ruminative, or obsessive) involving specific thought content - thoughts of death, dying, suicide as well as thoughts about specific ways of killing oneself (thoughts v. planning here).  Some include passive wishes for death, urges to kill or hurt oneself, and plans for suicide in their definition of suicidal ideation. Some include specific behaviors like collecting supplies, giving away belongings, and talking or writing about death and suicide in their definition of "ideation".

Here is a link to a good review article on instruments used to assess suicidal ideation. These provide the best insight, I think, into how the construct is defined. 

The DSM-5 glossary contains the following definition for suicidal ideation: "Thoughts about self-harm, with deliberate consideration or planning of possible techniques of causing one’s own death".

Bottom line - while the term 'suicidal ideation' isn't used very consistently in the literature, it does appear to represent a much broader set of ideas that just 'thoughts of suicide'. I agree with the decision to remove 'suicidal ideation' as a SYN for 'thoughts of suicide'. However, we do still need a concept for 'suicidal ideation'. 

Piper

I would agree with Piper's suggestion that suicidal ideation should be added and that it doesn't seem entirely synonymous with suicidal thoughts.  

In terms of my anecdotal clinical experience in the US, people typically chart text such as "- SI" for "no suicidal ideation" although they may also chart phrases such as "No suicidal thoughts, plans or intent."  I tried doing a PubMed search looking across all fields, not just title; with this approach suicidal ideation actually was the most commonly used term: "suicidal ideation" 11393 > "suicidal thoughts" 2304  > "suicide ideation" 1836 > "suicidal ideas" 243  > "suicide thoughts" 62

I would argue that the phrase "suicidal ideation" is in common enough use in the literature and in clinical practice that it should be available for people to select in a problem list.   

The next complication, however, is figuring out where suicidal ideation would belong in the hierarchy of parent and child terms.

The difficulty in getting a clear answer on this is an outgrowth of the lack of clarity in the field in terms of suicide related definitions as pointed out by numerous authors. Examples include: 

• Chappell et al. Assessment of Suicidal Ideation and Behavior: Report of the International Society for CNS Clinical Trials and Methodology Consensus Meeting. J Clin Psychiatry. 2017 Jun;78(6):e638-e647. https://www.ncbi.nlm.nih.gov/pubmed/28682533

• Meyer et al. Suicidality and risk of suicide--definition, drug safety concerns, and a necessary target for drug development: a consensus statement. J Clin Psychiatry. 2010 Aug;71(8): e1-e21. https://www.ncbi.nlm.nih.gov/pubmed/20797373

• Goodfellow et al. Contemporary Nomenclatures of Suicidal Behaviors: A Systematic Literature Review. Suicide Life Threat Behav. 2018 Jun;48(3):353-366. https://www.ncbi.nlm.nih.gov/pubmed/28485508

Further complicating the discussion, as Piper points out, is the whole concept of active vs. passive suicidal ideation.   Common definitions for these concepts are those used by Nock et al. (Patterns and predictors of persistence of suicide ideation: Results from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS). J Abnorm Psychol. 2018 Oct;127(7):650-658. https://www.ncbi.nlm.nih.gov/pubmed/30335437) in which they operationally define "active SI" as "ever have thoughts of killing yourself" or "passive SI"  as "ever wish you were dead or would go to sleep and never wake up".  These concepts of active vs. passive SI are also commonly used in clinical settings.   However, only active SI seems akin to having had a suicidal thought, per se. 

The other confound relates to suicidal behaviors where the CDC (Crosby AE, Ortega L, Melanson C. Self-directed violence surveillance: uniform definitions and recommended data elements, version 1.0. Atlanta, GA: US Department of Health and Human Services, CDC; 2011. [Accessed June 11, 2012]. Available at: http://www.cdc.gov/violenceprevention/pdf/Self-Directed-Violence-a.pdf.) and others (US Department of Veterans Affairs. Mental Illness Research, Education and Clinical Centers Veterans Integrated Service Network 19. [Accessed on 1 July 2013];Self-Directed Violence Classification System. Available at: http://www.mirecc.va.gov/visn19/education/nomenclature.asp.) have chosen to use a framework that refers to suicidal vs. non-suicidal self-directed violence.  However, they do not seem to provide definitions that relate only to ideation/thoughts. 

The Meyer et al., paper ( J Clin Psychiatry. 2010 Aug;71(8): e1-e21.) noted specifically that "Suicidal ideation, suicidal behavior, and suicide are preferable terms; operational definitions for these terms should be formulated and disseminated and should work in translation across languages and cultures" and that "Suicidality should be abandoned as a term" since it is "not as clinically useful as more specific terminology (ideation, behavior, attempts, and suicide)."

The article that Piper mentioned (Batterham et al. A systematic review and evaluation of measures for suicidal ideation and behaviors in population-based research. Psychol Assess. 2015 Jun;27(2):501-512.  https://www.ncbi.nlm.nih.gov/pubmed/25496086) gives a nice overview of scales for population studies but doesn't come to firm conclusions as to an optimal scale.  They also base a number of their criteria on pragmatic considerations such as scale validity, length and availability. However, they aren't comparing/constrasting definitions of terms per se.