Does Your Academic Training Destine Your Choice of Research Subject?


As I’ve been discussing the biomedical research workforce with people in the extramural community over the past few months, I’ve heard people say things like “PhDs don’t do much research with human subjects”. I decided to look into data that could support or refute statements such as this, and started with checking data on the use of animal and human subjects in research.

As you can see in the graphs below, we looked at awards by degree over the past 10 years and grouped them into four categories based on the research described in the grant applications: 1) human subjects research only (defined as having been reviewed by an Institutional Review Board), 2) animal subjects research only (defined as having been reviewed and approved by an Institutional Animal Care and Use Committee), 3) no human or animal subjects, or 4) both human and animal subjects.

To put these data in context, you’ll remember that about 70% of NIH-funded PIs have PhDs, with most of the remaining PIs having either an MD or an MD/PhD. Since the number of PIs with other degrees (DDS or DVM only, for instance) is very small, we’ve provided those data separately – see the footnote below.

First, we took a look at human and animal subject use by each degree category: PhDs, MD/PhDs, and MD.  As shown in figure 1, among PIs with a PhD degree, about 45% of PhDs engage in research involving only animal subjects, about 22% engage in human subjects research, a little less than 30% do research with no human or animal subjects, and only 5% conduct research with both. These proportions haven’t changed much over time.  Figure 1: RPG Awards Involving Human and/or Animal Subjects for Principal Investigators with PhD Degrees

The breakdown for PIs with MD/PhD degrees is slightly different (figure 2).  A higher proportion – over 50% – engage in research with animal subjects only, nearly 22% conduct research involving human subjects only, while around 10% do research with no human or animal subjects and another 10% with both.Figure 2: RPG Awards Involving Human and/or Animal Subjects for Principal Investigators with MD-PhD Degrees

Looking at PIs with MD degrees, we see MDs are likely to engage in research solely involving human subjects (approximately 45%), and also likely to engage in research involving only animal subjects (nearly 35%). However, they are the  least likely to conduct research that involves no human or animal subjects – only about 8% of MDs conduct research that does not involve human or animal subjects (figure 3).Figure 3: RPG Awards Involving Human and/or Animal Subjects for Principal Investigators with MD Degrees

In this last graph we’ve pulled out the human subjects only percentages for each of these 3 degree categories and compared them all on one graph. As shown in figure 4, investigators with MD degrees do tend to work on research involving only human subjects. This is not too surprising, though it is interesting that such a significant and similar percentage of PIs with a PhD and MD/PhD do research exclusively with human subjects.Figure 4: RPG Awards Involving Human Subjects Only By Degree Type

Taken together, these data support the idea that many PIs are conducting research that fits with their academic training, but a substantial number of PhD-trained scientists are doing research with human subjects and many clinician-scientists (either MDs or MD/PhDs) conduct research with neither human nor animal subjects.  Also, changes in the extramural community over the past decade do not seem to have affected these proportions significantly.  These data may prove useful to the new advisory committee to the director’s working group on clinician-scientists.


Note: The data table corresponding to these figures is posted on RePORT and can be downloaded in an Excel file. The table includes data for other advanced degrees (e.g. DVM, DDS, and DMD), which were not plotted on the charts because of their small numbers.


  1. It would be interesting to see a graph showing the percent of all NIH funded research that falls into the animal use only, the human use only, the human-animal, and the no human-no animal categories. Perhaps this graph exists elsewhere.

  2. The title hints at some very dangerous thinking. PhD does not equal training in non-human subjects research. There are many domains in which PhDs are trained to do work involving human subjects. From deep gene sequencing to behavior. It would be unfortunate to conclude that shifting the MD/PhD balance is the only way to increase human subjects research. Better to identify those programs/labs that train PhDs to do human subjects research.

  3. Interesting ! I do feel sometimes that PhD should involved some human subjects.. but it depends on what we look for though..Good to know this!

  4. I agree with the first comment that it would be interesting to see the breakdown on the number of projects that are human, animal, both, or neither, rather than by PI degree. I am a PhD who has done each of those kinds of projects but currently performs on research only with humans. We do exercise, dietary, and behavioral interventions and measure a variety of clinical and basic science outcomes. From past experience I know that many study teams like ours have a mix of MD and PhD (and RN and MS) personnel working on the project, especially when there is translational work and both bedside and benchtop pieces are involved. The degree of the PI is not so important in that case– the PI may just be the most senior, the best organizer, and/or the idea generator. Rather it is the make up of the collaborative team that is key.

  5. I agree with other posters that an MD vs. PhD dichotomy isn’t all that informative. MD is a pretty narrow training in terms of its focus, whereas PhD ranges widely in its focus. There are some areas of PhD that are highly human subjects focused (e.g., clinical psychology), whereas others not so much.

  6. Is there a breakdown nationally of PhD numbers across neuroscience, mathematics, engineering, psychology, sociology, and how those numbers affect the baselines you are talking about here? You’re saying most NIH grants awarded to PhDs are for animal research; are most of the PhDs applying for NIH grants coming from neuroscience programs, while the PhDs in engineering, psychology, and sociology are either outnumbered nationally, or apply to other sources?

  7. The data for the breakdown by degrees also suggests that those with PhDs may be more interested in research on fundamental questions that are not readily addressed at the organismal level than MDs. This isn’t unexpected. Alternatively, other considerations might disincline MDs to this type of research.

    The data may also reflect the appropriate balance of such fundamental research within the mission of the NIH.

  8. I think this is a preliminary indication of some of the problems associated with research PhDs or MDs, and should be interpreted with great caution. In addition, I think it might help to evaluate whether study sections approve of PhDs doing research with human subjects. I conduct research with both human and animal subjects, but have encountered significant criticism when trying to get human studies funded–not necessarily because I am a PhD (though I do think bias is a concern), but because it is often perceived that either the animal work automatically applies to humans (making the work unnecessary in human subjects), or that the work can’t be done in human subjects because it is difficult to do mechanistic studies (among many additional problems inherent in the peer review system). There are so many observations in animals that need to be confirmed in human subjects before we can approach mechanisms. For example, one of my grant applications scored poorly because animal work indicated that IL-17 is critical to development of disease in an animal model of multiple sclerosis, and the reviewers erroneously assumed that this was correct in humans. At that time, not one paper was published on IL-17 in MS patients! The field is still handicapped by this problem. In addition, add-on mechanistic studies to existing clinical trials in MS (and I suspect other diseases) are poorly funded, in spite of the intent of NIH to support them. It is my belief that MDs and PhDs need to put biases aside and work together to find common ground so that the focus can be concentrated on the real goal: productive research designed to help patients by revealing clinically significant disease mechanisms, responses to existing treatments and development of new, more effective treatments.

  9. While the analysis is interesting, the basic premise of the query is faulty. It’s erroneous to assume that PhD-driven research is synonymous with bench science. I recommend an NIH portfolio review cross-tabbed with domain of doctoral degree.

  10. It is absurd to think that all PhDs are basic scientists, just as it’s absurd to assume that all MDs can do clinical research. I have a PhD and trained exclusively with human subjects. I am not a psychologist and I have never worked with animals or been involved with bench work (other than to observe how some assays are done) in my entire career. I am NIH funded for my work, which has made significant steps toward improving diagnosis and treatment for many patients. Less focus should be given to the letters after a name; rather we should be concerned about how well equipped/experienced the PI and team are to conduct a well-designed study that has high likelihood of a positive impact on clinical care.

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