Htydjtk

My significant other (SO) and I are in five years of relationship. We met working in a lab and she already earned her PhD at that time. I was a graduate student. She was my supervisor after my adviser and she oversaw my project and helped me the process throughout. We now have two publications together. We worked professionally together for almost three years. She knows my potential both personally and professionally.

I am wondering if it is okay to use a letter of recommendation from her to apply for a PhD program.

No. If she discloses your relationship in the letter, the reviewer will likely disregard the letter completely, and may question your judgment for having asked her for a letter. If she does not disclose your relationship in the letter, that is a serious enough omission that it could have consequences for you later on (I can't quite tell where you are in your career, but the more senior you are, the more severe these consequences could be).

I'm going to come in with a no. (See edit remark at the end).

I originally said cautious yes. You can use a letter from your SO, with some caveats, as follows:

1. It should be an extra letter. Like, if they asked for at least 3, your SO should write the 4th.




2. If your SO is a postdoc at this time, the letter is already not worth that much, so after discounting for SO conflict of interest it might not be worth it.




3. The answer from cag51 is correct that your SO must disclose that you are in a relationship.




4. Given the nature of your relationship, your SO should make a huge effort to write a balanced letter, including your weaknesses / where you have room for improvement. If I read a letter from an SO that seemed honest, I might weight it even higher than another because the SO knows the applicant better than other letter writers.

So, after taking all that into account, should you still use your SO as a reference? Probably not. But as someone involved in admissions into PhD programs, I understand that in lab relationships happen, and I would be interested to hear what an SO had to say.

edit: It seems I'm more open minded about these things than other people in academia. There is a risk that having your SO send a letter will offend someone on the admissions committee, or be taken as a sign of bad judgement on your part. So the safe thing to do is to avoid using an SO (or any immediate relative) as a letter writer.

Look at things from another perspective:
Suppose, you use the letter with full disclosure of your relationship.
Suppose, you get admitted to the program. Suppose, somebody who didn’t get admitted finds out that you got admitted based on a recommendation letter from your SO¹.
Suppose that somebody causes a ruckus about this, be it legally, internally, or publicly.

Now put yourself in the position of the decision maker who is handling your application and is aware of the possibility of the above scenario.
The decision maker knows that it might be easily their head that rolls if it comes to the above situation.
Even if they have not read the recommendation letter, they cannot provide evidence that they didn’t².
It’s far safer for the decision maker to just reject your application.
Using a recommendation letter from an SO gives them an easy argument for this.

In case there is no disclosure, this might be an career ender for you and your SO due to not disclosing a blatant conflict of interest.
I can even imagine that you may even face criminal charges (e.g., if there are rules that compels you to declare any conflicts of interest, etc.).

<sup>¹ For example because your relationship ends badly, and your SO wants to take revenge.

² In exceptional circumstances such as pre-vetted applications, they may, but that’s nothing you can predict.</sup>

I'm going to say yes, but, there is a conflict here. If no one else has worked with you this much, then perhaps it is not the worst choice. If this loved one writes a letter they must disclose their relationship to you, and stick to facts, such as how many papers you've written, grants you've gotten, your punctuality and relationship with peers etc. and how you would fit well into the position. They should avoid generally complimenting you as a person as this is too open to interpretation perhaps.