Development and validation of the Trust in Multidimensional Healthcare Systems Scale (TIMHSS).

CONTEXT: The COVID-19 pandemic has reignited a commitment from the health policy and health services research communities to rebuilding trust in healthcare and created a renewed appetite for measures of trust for system monitoring and evaluation. The aim of the present paper was to develop a multidimensional measure of trust in healthcare that: (1) Is responsive to the conceptual and methodological limitations of existing measures; (2) Can be used to identify systemic explanations for lower levels of trust in equity-deserving populations; (3) Can be used to design and evaluate interventions aiming to (re)build trust. METHODS: We conducted a 2021 review of existing measures of trust in healthcare, 72 qualitative interviews (Aug-Dec 2021; oversampling for equity-deserving populations), an expert review consensus process (Oct 2021), and factor analyses and validation testing based on two waves of survey data (Nov 2021, n = 694; Jan-Feb 2022, n = 740 respectively). FINDINGS: We present the Trust in Multidimensional Healthcare Systems Scale (TIMHSS); a 38-item correlated three-factor measure of trust in doctors, policies, and the system. Measurement of invariance tests suggest that the TIMHSS can also be reliably administered to diverse populations. CONCLUSIONS: This global measure of trust in healthcare can be used to measure trust over time at a population level, or used within specific subpopulations, to inform interventions to (re)build trust. It can also be used within a clinical setting to provide a stronger evidence base for associations between trust and therapeutic outcomes.

Functional in vitro diversity of an intrinsically disordered plant protein during freeze-thawing is encoded by its structural plasticity.

Intrinsically disordered late embryogenesis abundant (LEA) proteins play a central role in the tolerance of plants and other organisms to dehydration brought upon, for example, by freezing temperatures, high salt concentration, drought or desiccation, and many LEA proteins have been found to stabilize dehydration-sensitive cellular structures. Their conformational ensembles are highly sensitive to the environment, allowing them to undergo conformational changes and adopt ordered secondary and quaternary structures and to participate in formation of membraneless organelles. In an interdisciplinary approach, we discovered how the functional diversity of the Arabidopsis thaliana LEA protein COR15A found in vitro is encoded in its structural repertoire, with the stabilization of membranes being achieved at the level of secondary structure and the stabilization of enzymes accomplished by the formation of oligomeric complexes. We provide molecular details on intra- and inter-monomeric helix-helix interactions, demonstrate how oligomerization is driven by an α-helical molecular recognition feature (α-MoRF) and provide a rationale that the formation of noncanonical, loosely packed, right-handed coiled-coils might be a recurring theme for homo- and hetero-oligomerization of LEA proteins.

Excess deaths in China during SARS-CoV-2 viral waves in 2022-2023.

Background: The extent to which the Omicron variant of SARS-CoV-2 raised death rates in China during its viral wave of December 2022-January 2023 remains largely undocumented. Methods: We worked with an established national survey organization to survey 8,004 adults in all 31 administrative areas of China to ask about deaths in families since January 2020. We examined age-specific death rates, focusing on deaths above age 60 years, and at 15-59 years. We compared these to the United Nations (UN) estimates of age-specific mortality in 2019. Findings: The survey participants were broadly similar to the 2020 census and other national surveys in age, sex, region, and smoking status, but had lower SARS-CoV-2 vaccination rates and higher education levels. There were no differences in reporting of deaths during the Omicron period (after November 2021) versus earlier. The survey captured 456 deaths, of which 329 occurred at ages 60+ years and 212 were of women. At ages 60+ years, death rates approximately doubled during December 2022-January 2023. Deaths at ages 15-59 years did not rise appreciably. The UN estimates approximately 675,000 deaths per month at ages 60+ years in 2019. If rates doubled nationally as in our survey, China had approximately 1.35 million excess deaths from December 2022-January 2023. Interpretation: China experienced a sharp but short increase in excess deaths among its elderly during the Omicron wave. If death registry data corroborate our estimates of substantial excess deaths in China, the worldwide estimates of excess deaths due to SARS-CoV-2 in 2022-2023 may need upward adjustment.

Smoking Cessation and Short- and Longer-Term Mortality.

Smoking Cessation and MortalityIn this meta-analysis of four national cohorts (total of 1.48 million adults followed for 15 years, in whom 122,697 deaths occurred), current smokers had higher hazard ratios for death compared with never smokers (2.8 for women, 2.7 for men). Survival between 40 and 79 years of age was 13 years less in people who smoked compared with never smokers. Former smokers showed lower hazard ratios (1.3 in both women and men). Cessation at every age was associated with longer survival, with benefits evident as early as 3 years after cessation.

Nivolumab Plus 5-Azacitidine in Pediatric Relapsed/Refractory Acute Myeloid Leukemia (AML): Phase I/II Trial Results from the Therapeutic Advances in Childhood Leukemia and Lymphoma (TACL) Consortium.

Improvements in survival have been made over the past two decades for childhood acute myeloid leukemia (AML), but the approximately 40% of patients who relapse continue to have poor outcomes. A combination of checkpoint-inhibitor nivolumab and azacitidine has demonstrated improvements in median survival in adults with AML. This phase I/II study with nivolumab and azacitidine in children with relapsed/refractory AML (NCT03825367) was conducted through the Therapeutic Advances in Childhood Leukemia & Lymphoma consortium. Thirteen patients, median age 13.7 years, were enrolled. Patients had refractory disease with multiple reinduction attempts. Twelve evaluable patients were treated at the recommended phase II dose (established at dose level 1, 3 mg/kg/dose). Four patients (33%) maintained stable disease. This combination was well tolerated, with no dose-limiting toxicities observed. Grade 3-4 adverse events (AEs) were primarily hematological. Febrile neutropenia was the most common AE ≥ grade 3. A trend to improved quality of life was noted. Increases in CD8+ T cells and reductions in CD4+/CD8+ T cells and demethylation were observed. The combination was well tolerated and had an acceptable safety profile in pediatric patients with relapsed/refractory AML. Future studies might explore this combination for the maintenance of remission in children with AML at high risk of relapse.

Adolescent Residential Addiction Treatment In The US: Uneven Access, Waitlists, And High Costs.

Drug overdose deaths among adolescents are increasing in the United States. Residential treatment facilities are one treatment option for adolescents with substance use disorders, yet little is known about their accessibility or cost. Using the Substance Abuse and Mental Health Services Administration's treatment locator and search engine advertising data, we identified 160 residential addiction treatment facilities that treated adolescents with opioid use disorder as of December 2022. We called facilities while role-playing as the aunt or uncle of a sixteen-year-old child with a recent nonfatal overdose, to inquire about policies and costs. Eighty-seven facilities (54.4 percent) had a bed immediately available. Among sites with a waitlist, the mean wait time for a bed was 28.4 days. Of facilities providing cost information, the mean cost of treatment per day was $878. Daily costs among for-profit facilities were triple those of nonprofit facilities. Half of facilities required up-front payment by self-pay patients. The mean up-front cost was $28,731. We were unable to identify any facilities for adolescents in ten states or Washington, D.C. Access to adolescent residential addiction treatment centers in the United States is limited and costly.

Distinct ancient structural polymorphisms control heterodichogamy in walnuts and hickories.

The maintenance of stable mating type polymorphisms is a classic example of balancing selection, underlying the nearly ubiquitous 50/50 sex ratio in species with separate sexes. One lesser known but intriguing example of a balanced mating polymorphism in angiosperms is heterodichogamy - polymorphism for opposing directions of dichogamy (temporal separation of male and female function in hermaphrodites) within a flowering season. This mating system is common throughout Juglandaceae, the family that includes globally important and iconic nut and timber crops - walnuts (Juglans), as well as pecan and other hickories (Carya). In both genera, heterodichogamy is controlled by a single dominant allele. We fine-map the locus in each genus, and find two ancient (>50 Mya) structural variants involving different genes that both segregate as genus-wide trans-species polymorphisms. The Juglans locus maps to a ca. 20 kb structural variant adjacent to a probable trehalose phosphate phosphatase (TPPD-1), homologs of which regulate floral development in model systems. TPPD-1 is differentially expressed between morphs in developing male flowers, with increased allele-specific expression of the dominant haplotype copy. Across species, the dominant haplotype contains a tandem array of duplicated sequence motifs, part of which is an inverted copy of the TPPD-1 3' UTR. These repeats generate various distinct small RNAs matching sequences within the 3' UTR and further downstream. In contrast to the single-gene Juglans locus, the Carya heterodichogamy locus maps to a ca. 200-450 kb cluster of tightly linked polymorphisms across 20 genes, some of which have known roles in flowering and are differentially expressed between morphs in developing flowers. The dominant haplotype in pecan, which is nearly always heterozygous and appears to rarely recombine, shows markedly reduced genetic diversity and is over twice as long as its recessive counterpart due to accumulation of various types of transposable elements. We did not detect either genetic system in other heterodichogamous genera within Juglandaceae, suggesting that additional genetic systems for heterodichogamy may yet remain undiscovered.

Transcriptomic Evidence of a Link between Cell Wall Biogenesis, Pathogenesis, and Vigor in Walnut Root and Trunk Diseases.

Crown gall disease (Agrobacterium tumefaciens), crown/root rot disease (Phytophthora spp.), root lesion disease (Pratylenchus vulnus) and tree vigor are key traits affecting the productivity and quality of walnuts in California. Unchallenged hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits. Enrichment analysis of the differentially expressed genes revealed that the increased expression of cell wall biogenesis-related genes plays a key role in susceptibility to A. tumefaciens, susceptibility to Phytophthora spp. and increased vigor. Analysis of the predicted subcellular loci of the encoded proteins revealed that many gene products associated with vigor and susceptibility were targeted to the plasma membrane and extracellular space, connecting these traits to sustaining barrier function. We observed that RNA processing and splicing, along with predicted nuclear targeting, were associated with resistance to A. tumefaciens, resistance to Phytophthora spp. and low vigor. Four genes within the J. microcarpa QTL region for resistance to A. tumefaciens and Phytophthora spp. were represented among our transcripts, with two of the genes being differentially expressed in association with resistance to A. tumefaciens and decreased vigor. No differential expression related to Phytophthora spp. or P. vulnus resistance was observed in this region. Additionally, the J. microcarpa haplotype expressed more transcripts associated with resistance to A. tumefaciens, Phytophthora spp. and low vigor, but not P. vulnus, than the J. regia haplotype. We also report unique and shared hormone and defense responses associated with each trait. This research suggests a link between cell wall biogenesis, vigor and critical root diseases of walnut.

A Bayesian approach to estimating COVID-19 incidence and infection fatality rates.

Naive estimates of incidence and infection fatality rates (IFR) of coronavirus disease 2019 suffer from a variety of biases, many of which relate to preferential testing. This has motivated epidemiologists from around the globe to conduct serosurveys that measure the immunity of individuals by testing for the presence of SARS-CoV-2 antibodies in the blood. These quantitative measures (titer values) are then used as a proxy for previous or current infection. However, statistical methods that use this data to its full potential have yet to be developed. Previous researchers have discretized these continuous values, discarding potentially useful information. In this article, we demonstrate how multivariate mixture models can be used in combination with post-stratification to estimate cumulative incidence and IFR in an approximate Bayesian framework without discretization. In doing so, we account for uncertainty from both the estimated number of infections and incomplete deaths data to provide estimates of IFR. This method is demonstrated using data from the Action to Beat Coronavirus erosurvey in Canada.

Development and validation of the Trust in Government measure (TGM).

BACKGROUND: Trust in government is associated with health behaviours and is an important consideration in population health interventions. While there is a reported decline in public trust in government across OECD countries, the tools used to measure trust are limited in their use for informing action to (re)build trust, and have limitations related to reliability and validity. To address the limitations of existing measures available to track public trust, the aim of the present work was to develop a new measure of trust in government. METHODS: Fifty-six qualitative interviews (Aug-Oct 2021; oversampling for equity-deserving populations) were conducted to design a national survey, including factor analyses and validation testing (N = 878; June 1-14th 2022) in Canada. RESULTS: The measure demonstrated strong internal consistency (α = 0.96) and test validity (CFI = 0.96, RMSEA = 0.09, SRMR = 0.03), suggesting that trust in government can be measured as a single underlying construct. It also demonstrated strong criterion validity, as measured by significant (p < 0.0001) associations of scores with vaccine hesitancy, vaccine conspiracy beliefs, COVID-19 conspiracy beliefs, trust in public health messaging about COVID-19, and trust in public health advice about COVID-19. We present the Trust in Government Measure (TGM); a 13-item unidimensional measure of trust in Federal government. CONCLUSIONS: This measure can be used within high-income countries, particularly member countries within the OECD already in support of using tools to collect, publish and compare statistics. Our measure should be used by researchers and policy makers to measure trust in government as a key indicator of societal and public health.

Informing efforts beyond tailored promotional campaigns by understanding contextual factors shaping vaccine hesitancy among equity-deserving populations in Canada: an exploratory qualitative study.

BACKGROUND: Vaccine hesitancy exists on a continuum ranging between complete adherence and complete refusal due to doubts or concerns within a heterogeneous group of individuals. Despite widespread acknowledgement of the contextual factors influencing attitudes and beliefs shaping COVID-19 vaccine hesitancy, qualitative research with equity-deserving groups, accounting for unique lived experiences, remains a gap in the literature. We aim to identify and begin to understand and document the unique contextual factors shaping hesitancy by equity-deserving groups as it relates to relationships with government and health authorities. METHODS: Participants were recruited and interviewed between Aug-Dec 2021. Semi-structured interviews using a convergent interviewing technique were conducted with individuals from the general population, as well as individuals who identify as First Nations, Métis, or Inuit, members of the LGBT2SQ + community, low-income Canadians, Black Canadians, and newcomers. Interviews were audio recorded and transcribed by a team of researchers. Memos were written following interviews and used to complement the thematic analysis of the interview data. Themes are presented in the results section. RESULTS: The rationale for hesitancy among equity-deserving groups is consistent with literature documenting hesitancy in the general population. Contextual factors surrounding equity-deserving groups' attitudes and beliefs, however, are unique and relate to a history of oppression, discrimination, and genocide. We identified factors unique to subgroups; for example, religious or fatalistic beliefs among participant who identify as FNMI, fear associated with lack of testing and speed of vaccines' production among participants who identify as FNMI, Black, and LGBT2SQ + , distrust of the healthcare system for LGBT2SQ + and Black Canadians, and distrust of the government and opposition to vaccine mandates for participating who identify as LGBT2SQ + , low-income, FNMI, or Black Canadian. Newcomers stood out as very trusting of the government and accepting of COVID-19 vaccination. CONCLUSIONS: While our data on vaccine hesitancy largely mirror concerns reported in the vast body of literature citing rationale for COVID-19 hesitancy in high-income countries, the contextual factors identified in our work point to the need for wider systemic change. Our results may be used to support efforts, beyond tailored promotion campaigns, to support the confident acceptance of vaccines for COVID-19 and the acceptance of novel vaccines as future infectious diseases emerge.

Temporal transcriptome and metabolite analyses provide insights into the biochemical and physiological processes underlying endodormancy release in pistachio (Pistacia vera L.) flower buds.

Pistachio (Pistacia vera L.), an economically and nutritionally important tree crop, relies on winter chill for bud endodormancy break and subsequent blooming and nut production. However, insufficient winter chill poses an increasing challenge in pistachio growing regions. To gain a better understanding of the physiological and biochemical responses of endodormant pistachio buds to chilling accumulation, we investigated the global gene expression changes in flower buds of pistachio cv. Kerman that were cultivated at three different orchard locations and exposed to increasing durations of winter chill. The expression of genes encoding ß-1,3-glucanase and ß-amylase, enzymes responsible for breaking down callose (ß-1,3-glucan) and starch (α-1,4-glucan), respectively, increased during the endodormancy break of pistachio buds. This result suggested that the breakdown of callose obstructing stomata as well as the release of glucose from starch enables symplasmic trafficking and provides energy for bud endodormancy break and growth. Interestingly, as chilling accumulation increased, there was a decrease in the expression of nine-cis-epoxycarotenoid dioxygenase (NCED), encoding an enzyme that uses carotenoids as substrates and catalyzes the rate-limiting step in abscisic acid (ABA) biosynthesis. The decrease in NCED expression suggests ABA biosynthesis is suppressed, thus reducing inhibition of endodormancy break. The higher levels of carotenoid precursors and a decrease in ABA content in buds undergoing endodormancy break supports this suggestion. Collectively, the temporal transcriptome and biochemical analyses revealed that the degradation of structural (callose) and non-structural (starch) carbohydrates, along with the attenuation of ABA biosynthesis, are critical processes driving endodormancy break in pistachio buds.

Full-thickness resection device for management of lesions involving the appendiceal orifice: Systematic review and meta-analysis.

Background and study aims Endoscopic resection of lesions involving the appendiceal orifice is technically challenging and is commonly referred for surgical resection. However, post-resection appendicitis is a concern. Many studies have varying rates of post-procedure appendicitis. We aim to report the rate of post-resection appendicitis by performing a systematic review and meta-analysis. Methods Studies that involved the use of a full-thickness resection device (FTRD) for management of appendiceal polyps were included. The primary outcome was appendicitis after FTRD and a subgroup analysis was performed on studies that only included FTRD performed at the appendiceal orifice. Results Appendicitis was encountered in 15% (95%CI: [11-21]) of the patients with 61% (95% CI: [44-76]) requiring surgical management. Pooled rates of technical success, histologic FTR, and histologic R0 resection in this sub-group (n=123) were 92% (95% CI: [85-96]), 98% (95% CI: [93-100]), and 72% (95% CI: [64-84%]), respectively. Post-resection histopathological evaluation revealed a mean resected specimen size of 16.8 ± 5.4 mm, with non-neoplastic pathology in 9 (7%), adenomas in 103 (84%), adenomas + high-grade dysplasia (HGD) in nine (7%), and adenocarcinoma in two (2%). The pooled rate for non-appendicitis-related surgical management (technical failure and/or high-risk lesions) was 11 % (CI: 7-17). Conclusions FTRD appears to be an effective method for managing appendiceal lesions. However, appendicitis post-resection occurs in a non-trivial number of patients and the R0 resection rate in appendiceal lesions is only 72%. Therefore, caution should be employed in the use of this technique, considering the relative risks of surgical intervention in each patient.

Canadians' trust in government in a time of crisis: Does it matter?

The ability of governments and nations to handle crises and protect the lives of citizens is heavily dependent on the public's trust in their governments and related social institutions. The aim of the present research was to understand public trust in government during a time of crisis, drawing on interview data (N = 56) collected during the COVID-19 pandemic (2021). In addition to the general public (n = 11), participants were sampled to obtain diversity as it relates to identifying as First Nations, Métis, and Inuit (n = 7), LGBT2SQ+ (n = 5), low-income (n = 8), Black Canadians (n = 7), young adult (n = 8), and newcomers to Canada (n = 10). Data were coded in consideration of social theories of trust, and specifically the nature of trust between individuals and institutions working with government in pandemic management. Canadians' trust in government was shaped by perceptions of pandemic communication, as well as decision-making and implementation of countermeasures. Data suggest that although participants did not trust government, they were accepting of measures and messages as presented through government channels, pointing to the importance of (re)building trust in government. Perhaps more importantly however, data indicate that resources should be invested in monitoring and evaluating public perception of individuals and institutions generating the evidence-base used to guide government communication and decision-making to ensure trust is maintained. Theoretically, our work adds to our understanding of the nature of trust as it relates to the association between interpersonal and institutional trust, and also the nature of trust across institutions.

The evolution of SARS-CoV-2 seroprevalence in Canada: a time-series study, 2020-2023.

BACKGROUND: During the first year of the COVID-19 pandemic, the proportion of reported cases of COVID-19 among Canadians was under 6%. Although high vaccine coverage was achieved in Canada by fall 2021, the Omicron variant caused unprecedented numbers of infections, overwhelming testing capacity and making it difficult to quantify the trajectory of population immunity. METHODS: Using a time-series approach and data from more than 900 000 samples collected by 7 research studies collaborating with the COVID-19 Immunity Task Force (CITF), we estimated trends in SARS-CoV-2 seroprevalence owing to infection and vaccination for the Canadian population over 3 intervals: prevaccination (March to November 2020), vaccine roll-out (December 2020 to November 2021), and the arrival of the Omicron variant (December 2021 to March 2023). We also estimated seroprevalence by geographical region and age. RESULTS: By November 2021, 9.0% (95% credible interval [CrI] 7.3%-11%) of people in Canada had humoral immunity to SARS-CoV-2 from an infection. Seroprevalence increased rapidly after the arrival of the Omicron variant - by Mar. 15, 2023, 76% (95% CrI 74%-79%) of the population had detectable antibodies from infections. The rapid rise in infection-induced antibodies occurred across Canada and was most pronounced in younger age groups and in the Western provinces: Manitoba, Saskatchewan, Alberta and British Columbia. INTERPRETATION: Data up to March 2023 indicate that most people in Canada had acquired antibodies against SARS-CoV-2 through natural infection and vaccination. However, given variations in population seropositivity by age and geography, the potential for waning antibody levels, and new variants that may escape immunity, public health policy and clinical decisions should be tailored to local patterns of population immunity.

Climate warming increases extreme daily wildfire growth risk in California.

California has experienced enhanced extreme wildfire behaviour in recent years1-3, leading to substantial loss of life and property4,5. Some portion of the change in wildfire behaviour is attributable to anthropogenic climate warming, but formally quantifying this contribution is difficult because of numerous confounding factors6,7 and because wildfires are below the grid scale of global climate models. Here we use machine learning to quantify empirical relationships between temperature (as well as the influence of temperature on aridity) and the risk of extreme daily wildfire growth (>10,000 acres) in California and find that the influence of temperature on the risk is primarily mediated through its influence on fuel moisture. We use the uncovered relationships to estimate the changes in extreme daily wildfire growth risk under anthropogenic warming by subjecting historical fires from 2003 to 2020 to differing background climatological temperatures and aridity conditions. We find that the influence of anthropogenic warming on the risk of extreme daily wildfire growth varies appreciably on a fire-by-fire and day-by-day basis, depending on whether or not climate warming pushes conditions over certain thresholds of aridity, such as 1.5 kPa of vapour-pressure deficit and 10% dead fuel moisture. So far, anthropogenic warming has enhanced the aggregate expected frequency of extreme daily wildfire growth by 25% (5-95 range of 14-36%), on average, relative to preindustrial conditions. But for some fires, there was approximately no change, and for other fires, the enhancement has been as much as 461%. When historical fires are subjected to a range of projected end-of-century conditions, the aggregate expected frequency of extreme daily wildfire growth events increases by 59% (5-95 range of 47-71%) under a low SSP1-2.6 emissions scenario compared with an increase of 172% (5-95 range of 156-188%) under a very high SSP5-8.5 emissions scenario, relative to preindustrial conditions.

Change in patient-centered outcomes of psychological well-being, sleep, and suicidality following treatment with intravenous ketamine for late-life treatment-resistant depression.

OBJECTIVE: To examine whether psychological well-being, sleep, and suicidality improved with treatment with intravenous (IV) ketamine for late-life treatment-resistant depression (TRD). METHODS: This is an analysis of secondary outcomes in an open-label late-life TRD study examining the safety, tolerability, and feasibility of IV ketamine infusions. In the acute phase, participants (N = 25) aged 60 years or older received twice-a-week IV ketamine for 4 weeks. Then, participants with Montgomery-Asberg Depression Rating Scale (MADRS) total score <10 or ≥ 30% reduction from baseline proceeded to the continuation phase, an additional four weeks of once-a-week IV ketamine. The secondary outcomes analyzed here are based on the National Institute of Health Toolbox Psychological Well-Being subscales for Positive Affect and General Life Satisfaction, the Pittsburgh Sleep Quality Index, and the Scale for Suicidal Ideation. RESULTS: Psychological well-being, sleep, and suicidality improved during the acute phase and those improvements were sustained during the continuation phase. Greater improvements in measures of psychological well-being and sleep were seen in participants who had greater improvements in MADRS scores and moved onto the continuation phase. All but one of the few participants with high suicidality at baseline improved; there were no cases of treatment-emergent suicidality. CONCLUSIONS: Psychological well-being, sleep, and suicidality improved in participants with late-life TRD who received IV ketamine for 8 weeks. A future larger and longer controlled trial is needed to confirm and extend these findings. REGISTRATION: ClinicalTrials.gov identifier: NCT04504175.

Natural variation in photosynthesis and water use efficiency of locally adapted Persian walnut populations under drought stress and recovery.

Persian walnut is a drought-sensitive species with considerable genetic variation in the photosynthesis and water use efficiency of its populations, which is largely unexplored. Here, we aimed to elucidate changes in the efficiency of photosynthesis and water content using a diverse panel of 60 walnut families which were submitted to a progressive drought for 24 days, followed by two weeks of re-watering. Severe water-withholding reduced leaf relative water content (RWC) by 20%, net photosynthetic rate (Pn) by 50%, stomatal conductance (gs) by 60%, intercellular CO2 concentration (Ci) by 30%, and transpiration rate (Tr) by 50%, but improved water use efficiency (WUE) by 25%. Severe water-withholding also inhibited photosystem II functionality as indicated by reduced quantum yield of intersystem electron transport (φEo) and transfer of electrons per reaction center (ET0/RC), also enhanced accumulation of QA (VJ) resulted in the reduction of the photosynthetic performance (PIABS) and maximal quantum yield of PSII (FV/FM); while elevated quantum yield of energy dissipation (φDo), energy fluxes for absorption (ABS/RC) and dissipated energy flux (DI0/RC) in walnut families. Cluster analysis classified families into three main groups (tolerant, moderately tolerant, and sensitive), with the tolerant group from dry climates exhibiting lesser alterations in assessed parameters than the other groups. Multivariate analysis of phenotypic data demonstrated that RWC and biophysical parameters related to the chlorophyll fluorescence such as FV/FM, φEo, φDo, PIABS, ABS/RC, ET0/RC, and DI0/RC represent fast, robust and non-destructive biomarkers for walnut performance under drought stress. Finally, phenotype-environment association analysis showed significant correlation of some photosynthetic traits with geoclimatic factors, suggesting a key role of climate and geography in the adaptation of walnut to its habitat conditions.