Are there objective ways to measure narcissism?
The current diagnostic criteria of narcissistic personality disorder (NPD) requires five out of nine indicated signs (citing DSM-5; APA, 2013):

>1. Has a grandiose sense of self-importance
2. Is preoccupied with fantasies of unlimited success, power, brilliance, beauty, or ideal love
3. Believes s/he is special and unique and can only be understood/associate with other special or high status people/institutions
4. Requires excessive admiration
5. Has a sense of entitlement
6. interpersonally exploitative
7. Lacks empathy: is unwilling to recognize or identify with the feelings/needs of others
8. Is often envious of others and believes others are envious of him/her
9. Shows arrogant, haughty behavior/attitudes

To objectively measure narcissism, there are psychometric tests such as the Narcissistic Personality Scale for this matter. However, research advances challenge the lack of empathy in narcissistic people: stating that an identifying feature of NPD (lack of empathy) is probably misuderstood. So in essence, the tipping point that separates what is normal from what is narcissistic is being shaken again.

Is it when it becomes a problem for others? For ourselves?

This is generally correct, depending on the perspective. A clinically diagnosable disorder is generally defined as a condition that "causes clinically significant impairment in social, occupational, or other important areas of current functioning.(APA, 2013)" You can see that diagnostic criteria in most mental health disorders like mood disorders (depression), anxiety disorders, trauma-related disorders, etc.

However, this criteria isn't present in personality disorders. The unifying feature of personality disorders is that it has specific pervasive patterns of behavior that begins by early adulthood. That's it. I am convinced to think that your question is still under debate of researchers worldwide.

However, in practice, clients seek the diagnosis for personality disorders when it causes significant distress on them or on other people. So it becomes NPD (or other PD) when it becomes problematic.

This is really the key part of the study ^((and why I subscribed thru email for the release of the article)). Most people nowadays think that people with Narcissistic Personality Disorder (NPD) do not have empathy.

Research, however, proves otherwise. Affective aspects of empathy (involved in sharing emotions of others, and responding appropriately to others) show impairment, while cognitive empathy (understanding thought processes of others) appears preserved. People with NPD can understand why people act a certain way, and they theoretically use that knowledge to cover up their internal suffering - outwardly seen as being manipulative and having grandiose sense of self.

^((for those who does not like opening the actual article))

Abstract of the study:

>Narcissistic personality disorder is characterized by self-absorption, grandiosity, exploitation of others and lack of empathy. People with that disorder may switch from an overt form, mainly with grandiosity, to a covert presentation, with fears, hypersensitivity and dependence from others. Empathy represents a key point in detecting people affected by narcissistic personality disorder because, even if it is described as reduced, it plays a fundamental role in exploitation and manipulation. A systematic search of Literature without any language or time restriction, was performed combining thesaurus and free-search indexing terms related to Narcissistic personality disorder and empathy and produced 531 results. Fifty-two papers that analyzed possible issues in the empathic attitude of people with narcissistic personality disorder were included in this narrative review. Empathy is the capability of understating and feeling others emotions. It is not a unitary construct and can be distinguished in cognitive and affective. It might be channeled into prosocial and antisocial behaviors. A crucial trait identified in narcissistic empathy is affective dissonance that is closely related to rivalry as part of the dark tetrad (narcissism, machiavellianism, psychopathy, and sadism). Subjects affected by narcissistic personality disorder show greater impairment in affective aspects while their cognitive part of empathy appears preserved. Saving at least the cognitive aspects of empathy may contribute to therapeutic improvement of affective aspects.

Discussion:

>People affected by NPD show specific issues in empathy, but those difficulties are limited to its affective part. In fact, the cognitive portion seems preserved and essential for manipulative skill and exploitation of others.
>
>Subjects with NPD may experience those problems with affective empathy because they feel others’ emotions as threatening and dangerous and react with detachment to preserve their own personal integrity. In addition to exploitation, a lack of empathic affectivity appears associated with proneness to criminal behaviors, particularly when NPD coexists with antisocial traits, contributing to psychopathy.
>
>Furthermore, rivalry seems the key feature among the Dark Triad traits that supports callousness to its extreme pole embodied in “affective dissonance,” with contradictory affects in response to someone else’s feelings.
>
>That alarming evidence, in terms of social implications and patient’s wellbeing, is often accompanied by poor therapeutic approaches. NPD patients are often labeled as untreatable, but self-reflection as a first and fundamental approach may represent a key step in facilitating the comprehension of someone else’s feeling and a crucial gateway to treatment.

Limitations:

>Research on narcissistic personality disorder is limited. Patients affected by narcissistic personality disorder are often considered among the most difficult to be treated. The fragility of their ego together with the tendency to impulsivity often obstruct the possibility of access to dynamic psychotherapy, which is considered the best treatment option. The crucial point in the treatment of NPD patients is their will to be treated, which is fundamental in psychotherapy. Such patients often consider treatments as a personal failure and refuse it.
>
>Due to their label as untreatable, studies focused on the efficacy of psychotherapy in those patients are few and, consequently, those that analyze empathy and its correlates are even fewer.
>
>Furthermore, most of the research is led on western populations, probably due to the rise of this illness in western cultures. This might represent an additional limitation because results cannot be generalized.

Excerpts from the editorial:

>So, what did we learn? The authors found no evidence in the general (not high risk) population of changes in general mental health, except for a slight deterioration in symptoms of depression. The word “slight” is important here. Sun and colleagues used a metric called the standardised mean difference, or SMD, and found a deterioration in depression symptoms of 0.12 SMD after the onset of the pandemic. Formally, this means a deterioration of 0.12 standard deviations. Cohen, who invented the metric, developed it for randomised trials and estimated that SMD values less than 0.2 indicated a minimal effect, 0.2-0.5 a small effect, 0.5-0.8 a moderate effect, and 0.8 or more a large effect.2 This may be too simplistic, however, and values between 0.24 and 0.5 have generally been suggested to correspond to a minimal clinically relevant difference for trials in people with depression.3 Whether these cut-offs can be directly applied to general population studies, such as those in Sun and colleagues’ systematic review, is not yet clear.

​

>Some individuals or subgroups might experience larger deteriorations than the population mean. The authors identify women as a vulnerable subgroup for depression, anxiety, and general mental health, although deteriorations were still minimal or small on average. Media attention has often focused on the pandemic’s particular impact on young people, but this is not born out by the present study: parameters of anxiety, depression, and general mental health did not deteriorate significantly in young adults, adolescents, or children. Future updates of this systematic review, which the authors will post online as more evidence accrues (https://www.depressd.ca/covid-19-mental-health), could usefully examine other subgroups, such as socially marginalised individuals.

​

>Finally, while the present study clearly shows that we need not be overly concerned about the general population’s mental health in relation to the covid-19 pandemic, reported prevalence rates of mental health symptoms, especially among adolescents, are still concerningly high.101112 Pandemic or not, there is a strong need to provide preventive mental health interventions for those most at risk of poor mental health outcomes.

​

Please note that the editorial provided a link to the actual research (Comparison of mental health symptoms before and during the COVID-19 pandemic) and a link to a stakeholder's opinion (A patient's perspective on mental health and the pandemic). All links are free full-text access.